N*U INS! OF STAND & TECH

AlllOb 0 4 fl 4 70

iNDom 85—3147

Evaluation of the Thermal Integrity of

the Building Envelopes of Eight Federal

Office Buildings

Reference

NBS

PUBLICATIONS

by

Richard A. Grot

Y. May Chang

Stephen Weber

* •». VS '

Andrew K. Persily

Jin B. Fang

Lawrence S. Galowin SEPTEMBER 1985

UO

100

U5b

85-5147

1985

Renter for Building Technology

Jational Bureau of Standards

)epartment of Commerce

Saithersburg, MD 20899

Office of Design and Construction

Public Buildings Service

General Services Administration

Washington, DC 20405

NATIONAL BUREAU OF STANDARDS

LIBRARY NBSIR 85-3147

1 / * EVALUATION OF THE THERMAL INTEGRITY

OF THE BUILDING ENVELOPES OF EIGHT

FEDERAL OFFICE BUILDINGS

Richard A. Grot

Andrew K. Persily

Y. May Chang

Jin B. Fang

Stephen Weber

Lawrence S. Galowin

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Gaithersburg, MD 20899

September 1985

Prepared for Public Buildings Service

General Services Administration

Washington, DC 20405

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director

ABSTRACT

Diagnostic test methods were applied to eight federal office buildings in

order to assess the applicability of these measurement methods for

determining the thermal integrity of the building envelope. The eight

federal office buildings were located in Anchorage, AK; Ann Arbor, MI;

Columbia, SC; Fayetteville, AR; Huron, SD; Norfolk, VA; Pittsfield, MA and

Springfield, MA. These buildings ranged in size from 20,000 ft^ (1,900 m^)

for the building in Pittsfield to 520,000 ft^ (48,000 m^) for the Anchorage

Federal Building. They were all constructed within the last ten years.

The diagnostic tests which were applied to these buildings were ground

infrared thermographic inspection, aerial infrared thermographic

inspection, spot radiometry, air infiltration and ventilation rate

measurement using tracer gas decay, building tightness testing using fan

pressurization, component tightness testing, and measurement of the thermal

conductance of major wall sections using portable calorimeters and heat

flow meters. This report presents and discusses the results of these

tests

Key Words: Air infiltration, building diagnostics, building thermal

integrity, fan pressurization, field measurements,

spot radiometers, thermal bridges, thermographic inspection,

tracer gas techniques, U-value measurements.

i
EXECUTIVE SUMMARY

Background

The federal government presently owns and leases thousands of buildings

throughout the United States. The General Services Administration (GSA)

and other federal agencies are also constructing new buildings each year.

In recent years, an increasing awareness of energy use has led to greater

concern regarding energy consumption in existing buildings and the expected

energy use in new buildings. In fact. GSA has developed energy guidelines

for new buildings in units of Btu/ft^ (MJ/m^) per year. However, many new

and existing buildings consume excessive amounts of energy due, in part, to

thermal defects in their exterior envelopes. These defects are due to poor

construction practice, misunderstanding of construction specifications, and

deterioration of building materials, as well as specific design details

which lead to thermal breaks in the building envelope.

Several diagnostic techniques have been developed to evaluate the thermal

integrity of building envelopes. In order to investigate the

implementation of such diagnostic procedures the GSA had the National

Bureau of Standards (NBS) develop a multi-phased research effort. The

first phase was devoted to the development of in-situ and nondestructive

procedures that the GSA could use to evaluate the thermal integrity of

building envelopes. This effort was developed under guidelines of a peer

reiew group consisting of representatives from the GSA, the Departments of

Defense, Housing and Urban Development and Energy, and Public Works of

Canada, and resulted in a report which addresses measurement techniques,

inspection procedures and data anlaysis procedures [1],

In Phase II of the project, reported on in this document, the diagnostic

procedures developed in Phase I were applied to eight federal buildings

located throughout the United States. This group of buildings includes

four large buildings (over 100,000 square feet) and four small buildings

(less than 100,000 square feet), all of relatively recent construction.

The eight buildings, located in a range of climates, include:

Large

Anchorage, AK

Columbia, SC

Norfolk, VA

Springfield, MA

Small

Ann Arbor , MI

Fayetteville, AR

Huron , SD

Pittsfield, MA

All of the buildings, except the Fayetteville building, were constructed

after the GSA energy guidelines were in effect.

Seven different diagnostic techniques were applied to all or some of the

buildings in order to locate and/or quantify deficiencies in the thermal

integrity of the building envelopes. The techniques were applied by NBS

personnel or by subcontractors and include the following:

Ground-based infrared thermography for locating thermal defects in the

envelope

Aerial infrared thermography for locating defects in roof systems.

li
Spot radiometry for locating and quantifying thermal defects.

Tracer gas measurements of infiltration and ventilation rates.

Pressurization testing for measuring envelope airtightness.

Heat flowmeters and portable calorimeters for measuring wall thermal

conductance and quantifying the effects of thermal bridges.

These diagnostic techniques performed well in locating and quantifying the

defects in the thermal integrity of the eight building envelopes. The

results of the application of each technique are summarized below.

Ground-Based Infrared Thermography

Though seven of these eight federal office buildings were built to the new

federal energy guidelines, thermographic inspection revealed serious

defects in each building. Thermal defects in the insulation system were

observed to be in the range of 6 to 18 percent of the wall areas of these

buildings. Leakage around windows and seams were observed in all

buildings. Other thermal anomalies found in these buildings included

missing insulation in the wall, thermal bridges, defective ceiling and

floor insulation, and convection within insulation. Buildings with

overhangs and indentations appeared to have severe problems in those areas.

Thermographic inspections performed on commercial buildings are capable of

determining the thermal integrity of the building envelopes and detecting

defects in the mechanical system. For new buildings, thermography can be

used for quality control during construction. Had such inspections been

done on these buildings, most of the observed defects could have been

corrected at no cost to the building owner. After buildings are occupied,

thermographic inspections can still identify degradation of materials and

locations of poor performance of building envelopes. However, correction

of these defects at this stage are costly and only justified in extreme

cases

Aerial-Based Infrared Thermography

The quality of the aerial thermographic surveys produced by the three

private contractors indicated that aerial thermographic surveys can yield

information from which roof damage can be assessed. For detection of roof

anomalies on single buildings, the economic benefits of aerial thermography

have not been determined. For the multi-building complex or large areas,

aerial surveys have shown that many buildings can be evaluated by flyovers.

Since it is necessary to follow-up with walk-on inspections, the cost

factors for also conducting the aerial survey may not be justifiable. On

the other hand, the demonstration that all thermal roof problems on a building can be detected without an aerial survey should be undertaken. If

proven, cost savings by elimination of the aerial study may then be

realized.

Roof anomalies revealed through aerial infrared surveys are often not

related to deficiencies resulting from the roofing system. Instead, they are attributable to building system components or equipment. The analysis

of such sources requires building and roof inspections by experienced

and/or trained staff.

iii
Roof-top level inspections with infrared equipment were required to define

potential deficiencies. Other testing, such as core-sampling or water

content measurements in thermal insulation by destructive means was

recommended by contractors for evaluation of the extent of deterioration.

Thermography did not prove to be a useful tool for inspecting the inverted

membrane roof of the Anchorage federal building. It helped to detect the

beginning of water damage to a section of the roof of the federal building

in Columbia, SC. The repair of this area before extensive damage is done

would prevent the need for replacement of the roof system at a later date.

Spot Radiometry

Results from spot radiometer inspections performed on two office buildings

indicated there were larger errors in the results for surface components of

high R-values than those of low R-values. This may be due to the

sensitivity of the instrument as well as inappropriateness of the steady

state assumption used to derive the equations used for calculations.

However, the thermal resistance values provided qualitative indications of

the surface's thermal performance, though the absolute measurements lacked

accuracy. Due to the simplicity and portability of the spot radiometer, it

can be used to qualitatively evaluate regions of building envelope

components

Tracer Gas Measurements of Infiltration and Ventilation

The average natural air infiltration rates measured in these buildings

varied from 0.2 air changes per hour for the Huron federal building to 0.70

air changes per hour for the Ann Arbor federal building. The infiltration

component of the design heating load from these buildings ranged from 23%

for the uninsulated Fayetteville federal building to 61% for the new

Springfield federal building. In four of the buildings air infiltration

contributed to over 50% of the heating loads. Two of the federal

buildings, Anchorage and Huron, have low air infiltration rates (0.28 and

0.20 air changes per hour). However, even for these buildings air

infiltration was a very important part of the heating load.

Ventilation rates under occupied conditions were also measured in the eight

buildings. It was found that for hot and cold outside temperatures, the

buildings are operated at minimum ventilation levels to reduce space

conditioning loads. At mild temperatures, outside air is used to cool the

buildings and the ventilation rates increases significantly. The minimum

ventilation rates show little temperature dependence in most of the

buildings, but some of the buildings exhibit a dependence on wind speed.

When the minimum ventilation rates did vary with weather conditions, this

implied that uncontrolled air leakage or weather induced infiltration is a significant portion of the net ventilation rate. In most of the buildings,

the summer and winter minimum ventilation rates are similar, but in some buildings there is a notable difference between the two minimum ventilation

rates. The minimum ventilation rates were compared to minimum outside air

intake levels suggested by ASHRAE, and it was found that most of the

buildings were operated very close to or below the ASHRAE recommendation.

Two of the buildings were operated well below this recommended ventilation

rate. Local variations in air distribution and problems of ventilation

efficiency can lead to effective ventilation rates in specific areas of a

IV
building which are significantly lower than the average rate for the

building. Three of the buildings, Springfield, Ann Arbor and Columbia, had

minimum ventilation rates from 20 to 50% more than required, thus wasting

energy during periods of extreme weather.

Pressurization Testing of Airtightness

As part of this project, the airtightness of the envelopes were evaluated

using pressurization techniques. Seven of the buildings were subjected to

whole building pressurization tests and were found to possess airtightness

levels similar to tight houses in units of exchanges per hour at an induced

pressure difference. The airtightness of the buildings in units of flow

per envelope area were generally higher than for tight houses due to the

low surface to volume ratios of the federal buildings. Therefore, the

airtightness in exchanges per hour from the pressurization tests provides a misleading indication of the federal buildings' airtightness. A small

number of windows in six of the buildings were pressure tested

individually, and while a wide range of leakiness levels was evident, they

were generally leakier than a common window tightness standard. The

fraction of total building leakage associated with windows was calculated

to be about 10 to 20%, a percentage similar to that found in houses. The

large building infiltration model of Shaw and Tamura was applied to the

seven buildings which were pressure tested, and the predictions were lower

than the infiltration rates measured with tracer gas.

Thermal Resistance Measurements

Reliable thermal resistance values of building envelopes can be derived

from in-situ measurements of indoor-to-outdoor air temperature differences

and of heat flow across test structures, provided that the measurements are carried out over a sufficiently long period. A measurement period of at

least two days is recommended, but an entire week of data collection is

advisable when possible. Both the heat flow meters and the portable

calorimeter were found to be useful tools for measuring heat flow through

large, non-homogeneous building assemblies in the field. Wall thermal

resistances derived from data obtained using a portable calorimeter yield

lower values than those obtained with heat flow meters. This difference is

attributed to the additional heat flow through highly conductive framing

members in the structure. The thermal resistance values of masonry

exterior walls of seven of the buildings was found to vary widely, from

approximately 8 to 39 ft^-h-°F/Btu (2 to 7 m^-K/W). The measured thermal

resistances deviated from the design thermal resistances by an average of

14%, the worst case being 45%.

Heat Losses Due to Thermal Bridges

The inspection of the exterior envelope of four federal office buildings

using infrared thermography revealed the existence of thermal bridges. The

measurement of the heat flow through these thermal bridges using heat flow

meters showed that the heat flux at the thermal bridges were from 62 to

118% greater than the heat flux through the insulated sections of the

walls. Examination of thermograms and architectural drawings showed that

the thermal bridges represented from 9 to 18% of the buildings insulated

wall areas. Therefore, the thermal bridges increased the wall heat loss by

approximately 10 to 21% relative to the same wall structure without thermal

v
bridges. A two-dimensional finite difference heat flow model was used to

simulate the transient response of the thermal bridge representing an exterior wall/intermediate floor system. At points at which heat flow

measurements could be made, the model predicted the measured heat flux

well. Moreover, the model predicted even higher heat fluxes at other

points on the thermal bridge where measurements could not be made.

Therefore, the total contribution of thermal bridges to heat loss is

probably even greater, perhaps by a factor of two, than that cited above.

Additional experimental work is needed to confirm this possibility.

A brief summary of the findings of the diagnostic testing of each federal

office building follows:

Ancho rage

The Anchorage federal building uses about 28,500 Btu/yr*ft^ (89.8 kWh/yrm^) for space heating. This is a well constructed building which is tight

and well insulated - though air infiltration accounts for over 55% of the

building load. The major defect is the thermal bridging resulting from the

manner in which the precast panels were suspended (increasing the wall heat

loss by about 20%). The wall area in the section above the suspended

ceiling was not insulated to the same level as the wall area below the

suspended ceilings. This was done by design; however, it is not

justifiable from a heat transfer point of view. Visual inspection of the

roof showed many areas with separations and fissures in the rigid

insulation; however, limited heat flow measurement did not detect a serious

reduction in thermal resistance in the roof insulation system. During the

extreme winter conditions, this building is often operated with closed

dampers during occupied periods and has ventilation rates which are only

39% of those recommended by the ASHRAE ventilation standard for a building

with smokers.

Ann Arbor

This building is a very poor energy performer. It is consuming about

132,000 Btu/yr*ft^ (416 kWh/yr-m^) for space heating. It has a high air

infiltration rate of about 0.7 air changes per hour, which accounts for

about 48% of the building heating load. The building has over 14,000 ft^

(1,300 m^) of glass area which contributes to about 26% of the heat load.

The opaque walls constitute 18% of the heat load and the roof about 8%.

About 18% of the wall area showed thermal defects when inspected by

thermography. The thermal resistances of the wall section were close to

the predicted values when the insulation was properly installed. The

design of the building resulted in thermal bridging which increased the

wall heat loss by about 8%.

Columbia

The Columbia federal building uses about 20,035 Btu/yr’ft^ (63.1 kWh/yr-m^)

of energy for space heating. Air infiltration accounts for about 52% of

the space heating load (0.4 air changes per hour). Air conditioning

accounts for about 23% of the electrical energy use of the building. The

building has operable windows which are quite leaky and which account for

about 31% of the building leakage. About 17% of the wall area of the

building has thermal defects, the most serious of which was air penetration

vi
around the insulation. This was caused by the manner in which the steel

framing was installed in the building; an approximately one inch gap was left between the exterior concrete panels and the framing, and the

insulation was hung in the framing cavaties. The building also had thermal

bridging which increased the heat flow through the wall by about 10%. The

manner in which the insulation was installed in the wall area about the

suspended ceiling was incorrect, allowing air movement through the

insulation and leaving exposed exterior wall uninsulated. The minimum

ventilation rate of this building was 51% above that required for an office

building with smokers, thus adding to the space conditioning loads in

extreme weather conditions.

Fayetteville

The Fayetteville federal building uses about 30,000 Btu/ft^*yr (94.5

kWh/yr-m^) for space heating. It is basically an uninsulated building

built before the federal energy conservation guidelines were developed. In

terms of energy use per unit floor area per degree day it is the second

worst performer. The space heating load consists of 48% transmission

through the opaque walls, 25% through the glass, 23% by air infiltration

(0.33 air changes per hour) and 3% through the roof. The major deficiency

of the building is the existence of large, uninsulated wall areas including

large sections of spandrel glass. The building has serious leakage

problems at the interface of the glass and spandrel walls and the

structural columns. The first and fourth floors have serious leakage in

the overhangs in the return air plenum. The building has adequate minimum

ventilation; however, the ventilation rate is strongly wind dependent,

indicating that much of the ventilation is being supplied by air leakage

and not through the outside air supply ducts.

Huron

The Huron federal building used 21,514 Btu/ft^'yr (67.8 kWh/yr-m^) for

space heating. This building is the tightest building of the eight tested,

having an air infiltration rate of 0.2 air changes per hour. The space

heating load consists of 19% transmission through the glass area, 31%

through the opaque wall areas, 17% through the roof and 33% by air

infiltration. The framing members of the opaque wall increased the heat

flow by about 30% above the design value of the insulation. Thermal

bridging at the floor/wall interface caused another 10% increase in heat

flow through the opaque wall areas. The minimum ventilation rate of this

building was only 26% of the minimum requirements for a building with

smokers

Norfo lk

The Norfolk federal building uses about 10,588 Btu/ft^*yr (33.4 kWh/yr-m^)

of electricity (on-site) for space heating. The building heat loss

consists of 27% transmission through the glass areas, 15% through the

opaque wall areas, 6% through the roof and 15% by air infiltration (0.52

air changes per hour). The building had serious defects in the insulation

in the overhangs over the garage and front entrance. The thermal

resistance of the insulated walls was only 54% of the predicted values.

The minimum ventilation rate was 90% of that recommended for an office

building with smokers.

vn
Pittsfield

The federal building in Pittsfield, MA uses about 51,200 Btu/ft^* (161

kWh/yr-m^) for space heating. The largest component of the heat load is

air infiltration, accounting for 36% of the load (0.3 air changes per

hour). The opaque walls contribute about 22% of the heat transmission, the

roof 21% and the glass area 19%. The minimum ventilation rate of the

building is 90% of the requirement for a building with smokers.

Thermography showed that about 18% of the exterior wall area had defects,

the most serious being air penetration around the insulation. The measured

thermal resistance of the walls was about 13% less than the predicted

thermal resistance.

Springfield

The Springfield federal building was a newly constructed office building

and therefore there were no previous fuel records for the building.

Twenty-three percent of the heat loss of the building is due to

transmission through the glass areas, 11% through the opaque wall areas, 5%

through the roof and 61% by air infiltration (0.52 air changes per hour).

The insulation of the exterior walls consist of rigid foam insulation

applied to the concrete panels in such a way that air could leak around the

insulation and into the air cavity between the steel framing. The

effective thermal resistance of this wall construction was only 52% of the

predicted value. The ventilation and air infiltration rates of the

building had a strong temperature dependence which could be due to the

leakiness of the building or a ventilation system control problem.

vm
Acknowledgments

The authors wish to express their appreciation to Erma Striner and David

Eakin of the Public Building Service of the General Services Administration

for guidance and assistance throughout the project. The GSA staff at the

test sites also provided invaluable assistance in this project and the

authors acknowledge the following personnel: Anchorage - Building

Managers, Jesse Avila and Jack Froiland, Building Engineers, Paul Zinn and

Wes Young; Ann Arbor - Building Manager, Nils Strand, Building Engineer,

Bob Yeoman; Columbia - Building Managers, Jack Terry and Herb Drakeford;

Fayetteville - Building Manager, Neil Rogers, Building Engineer, Ken

Collier; Huron - Building Manager, George Green, Building Engineers, James

Round and Raul Rios; Norfolk - Building Managers, Thomas Coulboume and Lee

Smith, Building Engineer, Ed Akins; Pittsfield - Building Manager, Eugene

Raymond, Building Engineer, Allen Creel; Springfield - Building Manager,

Philip Haddad, Building Construction Engineer, Steve Mastoyin, Building

Engineer, Richard McCorkindale. The assistance of Doug Pruitt and Samuel

Silberstein of NBS was also instrumental in the completion of this project,

along with the efforts of Phil Engers, Charlene Frith, Pat Lane, Jay

Murphy, and Steven Schweinfurth. Very special thanks are expressed to

Robin Bickel for her efforts in preparing this report.

IX
Preface

This work was sponsored by the Public Building Service of the General

Services Administration through an interagency agreement with the National

Bureau of Standards, Interagency Agreement No. PBS-80-1.

x
Table of Contents

Abstract i

Executive Summary ii

Acknowledgments ix

Preface x

List of Figures xiii

List of Tables xvi

Introduction 1

Building Descriptions 6

Ground Infrared Thermographic Inspections 33

3.1 Background

3.2 Summary of Results

3.2.1 Description of Thermal Defects in the Anchorage

Federal Building

3.2.2 Description of Thermal Defects in the Ann Arbor

Federal Building

3.2.3 Description of Thermal Defects in the Columbia

Federal Building

3.2.4 Description of Thermal Defects in the Fayetteville

Federal Building

3.2.5 Description of Thermal Defects in the Huron

Federal Building

3.2.6 Description of Thermal Defects in the Norfolk

Federal Building

3.2.7 Description of Thermal Defects in the Pittsfield

Federal Building

3.2.8 Description of Thermal Defects in the Springfield

Federal Building

3.3 Conclusions

Aerial Infrared Thermographic Inspections 52

4.1 Introduction

4.2 Procurement of Aerial Thermographic Services

4.3 Evaluation of Roof System by Aerial Thermography

4.4 Conclusions

Audits Using Spot Radiometers 58

5.1 Introduction

5.2 Procurement of Audits Using Spot Radiometers

5.3 Thermal Resistance Measurements Using Spot Radiometers

5.4 Results of the Inspections of the Huron and Ann Arbor

Federal Buildings

5.5 Conclusions

Air Infiltration and Ventilation Measurements 66

6.1 Introduction

xi
6.2 Results of the Air Infiltration Tests

6.3 Measured Ventilation Rates

6.4 Minimum Ventilation Requirements

6.5 Ventilation Efficiency

6.6 Conclusions

7. Building Tightness Testing Using Pressurization 94

7.1 Introduction

7.2 Test Methods

7.3 Test Equipment

7.4 Details of Whole Building Pressurization

7.5 Whole Building Pressurization Results

7.6 Component Pressurization Results

7.7 Relation of Pressurization Tests to Infiltration Rates

7.8 Conclusions

8 . The Measurement of Envelope Thermal Resistance

8.1 Introduction

8.2 Instrumentation and Procedures

8.3 Test Results

8.4 Conclusions

110

9. Heat Losses Due to Thermal Bridges

9.1 Introduction

9.2 Description of the Thermal Bridges Found in the

Building Envelopes

9.3 Instrumentation and Procedures

9.4 Test Results

9.5 Mathematical Modeling

9.6 Conclusions

127

10. Summary and Conclusions 148

References 155

Appendix A - Economic Methodology for Selecting Optimal ... 158

Diagnostic Techniques for Federal Office

Buildings

Appendix B - Specifications for Aerial Infrared 171

Thermographic Roof Inspections

Appendix C - Specifications for Energy Audits with 174

Spot Radiometers for Temperature or Radios ity

Measurements

Xll
List of Figures

2.1 Location of the Eight Federal Office Buildings

2.2 Schematic Diagram and Photograph of Federal Building in Anchorage, AK

2.3 Schematic Diagram and Photograph of Federal Building in Ann Arbor, MI

2.4 Schematic Diagram and Photograph of Federal Building in Columbia, SC

2.5 Schematic Diagram and Photograph of Federal Building in Fayetteville,

AR

2.6 Schematic Diagram and Photograph of Federal Building in Huron, SD

2.7 Schematic Diagram and Photograph of Federal Building in Norfolk, VA

2.8 Schematic Diagram and Photograph of Federal Building in Pittsfield,

MA

2.9 Schematic Diagram and Photograph of Federal Building in Springfield,

MA

3.1 Sample Defects Observed in the Anchorage Federal Building

3.2 Thermal Defects Observed in the Anchorage Building

3.3 Sample Defects Observed in the Ann Arbor Federal Building

3.4 Thermal Defects Observed in the Ann Arbor Building

3.5 Sample Defects Observed in the Columbia Federal Building

3.6 Thermal Defects Observed in the Columbia Building

3.7 Sample Defects Observed in the Fayetteville Federal Building

3.8 Thermal Defects Observed in the Fayetteville Building

3.9 Sample Defects Observed in the Huron Federal Building

3.10 Thermal Defects Observed in the Huron Building

3.11 Sample Defects Observed in the Norfolk Federal Building

3.12 Thermal Defects Observed in the Norfolk Building

3.13 Sample Defects Observed in the Pittsfield Federal Building

3.14 Thermal Defects Observed in the Pittsfield Building

3.15 Sample Defects Observed in the Springfield Federal Building

3.16 Thermal Defects Observed in the Springfield Building

xiii
4.1 Heat Loss Area of the Springfield Roof System Observed by Aerial

Thermography

4.2 Aerial Photograph and Aerial Thermogram of the Columbia Building Roof

System

4.3 Photograph and Thermogram from Walk-on Infrared Survey of the

Columbia Building Roof System

4.4 Wet Polystyrene Insulation and Deterioration of the Anchorage

Building Roof System

5.1 Percentage Variation of Measured R-Values from Spot Radiometer Versus

Temperature Difference of Inside Air and Surface

5.2 Thermal Resistance (R-value) of Spot Radiometer Measurement Versus

Design for the Huron Building

6.1 Infiltration Rate Versus Temperature Difference

6.2 Infiltration Rate Versus Wind Speed

6.3 Ventilation Rate Versus Temperature Difference

6.4 Ventilation Rate Versus Wind Speed

7.1 Building Pressurization Testing Set-Up

7.2 Surface to Volume Ratios of Federal Buildings and Houses

7.3 Pressurization Test Results

7.4 Weather Induced Infiltration Rates Versus Pressurization Test Results

8.1 Construction Details of Portable Calorimeter

8.2 Schematic of the Measurement /Contro 1 System for the Portable

Calorimeter

8.3 Indoor and Outdoor Temperatures, Temperature Differences Across Wall

and Surface Heat Fluxes Measured with Heat Flux Transducers and the

Calorimeter

8.4 Long Term Variations of Heat Flux Transducer and Calorimeter

Measurements of a Wall Section

8.5 Long Term Variations of Thermal Resistance Measurements of the Upper

Wall and Structural Beam and Column

8.6 Effects of Measurement Period on Average Wall R-Values Determined by

Heat Flux Transducer and Calorimeter

8.7 Comparison Between the Measured Thermal Resistance and the Predicted

Steady-State Resistance Values

xiv
9.1 Thermal Bridges Found in the Exterior Wall of the Huron Office

9.2 Thermal Bridges Occurring in the Ann Arbor Building

9.3 Thermal Bridges Observed in the Upper Floors of the Anchorage

Building

9.4 Thermal Bridges Occurring in the Columbia Building

9.5 Construction Details and Sensor Locations on the Exterior Wall in the

Huron Office Building

9.6 Construction Details of the Exterior Wall in the Ann Arbor Office

Building

9.7 Construction Details of the Exterior Wall in the Anchorage Office

Building

9.8 Construction Details of the Exterior Wall in the Columbia Office

Building

9.9 Temperature and Heat Flux in the Huron Building as a Function of Time

9.10 Temperature and Heat Flux in the Ann Arbor Building as a Function of

Time

9.11 Temperature and Heat Flux in the Anchorage Building as a Function of

Time

9.12 Temperature and Heat Flux in the Columbia Building as a Function of

Time

9.13 Wall Thermal Resistance Values Plotted as a Function of the Length of

the Measurement Period for the Ann Arbor Building

9.14 Comparison of Calculated Heat Flux on the Inside Surface with

Measured Values

9.15 Calculated Outside Surface Heat Flux Distribution

10.1 Comparison of Transmission Losses and Energy Consumed for Each

Building

10.2 Comparison of Conduction Transmission Losses and Energy Consumed for

Each Building

xv
List of Tables

1.1 Schedule of Tests

2.1 Building Dimensions

2.2 Description of Typical Exterior Walls of Each Building

2.3 Description of Roof Insulation Systems

2.4 Thermal Characteristics of Building Envelope for Anchorage, AK

Federal Building

2.5 Thermal Characteristics of Building Envelope for Ann Arbor, MI

Federal Building

2.6 Thermal Characteristics of Building Envelope for Columbia, SC Federal

Building

2.7 Thermal Characteristics of Building Envelope for Fayetteville, AR

Federal Building

2.8 Thermal Characteristics of Building Envelope for Huron, SD Federal

Building

2.9 Thermal Characteristics of Building Envelope for Norfolk, VA Federal

Building

2.10 Thermal Characteristics of Building Envelope for Pittsfield, MA

Federal Building

2.11 Thermal Characteristics of Building Envelope for Springfield, MA

Federal Building

2.12 Air Handler Characteristics of HVAC System for Anchorage, AK Federal

Building

2.13 Air Handler Characteristics of HVAC System for Ann Arbor, MI Federal

Building

2.14 Air Handler Characteristics of HVAC System for Columbia, SC Federal

Building

2.15 Air Handler Characteristics of HVAC System for Fayetteville, AR

Federal Building

2.16 Air Handler Characteristics of HVAC System for Huron, SD Federal

Building

2.17 Air Handler Characteristics of HVAC System for Norfolk, VA Federal

Building

2.18 Air Handler Characteristics of HVAC System for Pittsfield, MA Federal

Building

xvi
2.19 Air Handler Characteristics of HVAC System for Springfield, MA

Federal Building

2.20 Degree Days for Building Sites

2.21 Power and Fuel Records for Federal Building in Anchorage, AK for

FY1981

2.22 Power and Fuel Records for Federal Building in Ann Arbor, MI for

FY1981

2.23 Power and Fuel Records for Federal Building in Columbia, SC for

FY1981

2.24 Power and Fuel Records for Federal Building in Fayetteville, AK for

FY1981

2.25 Power and Fuel Records for Federal Building in Huron, SD for FY1981

2.26 Power and Fuel Records for Federal Building in Norfolk, VA for FY1981

2.27 Power and Fuel Records for Federal Building in Pittsfield, MA for

FY1981

2.28 Base and Excess Electrical Loads for the Federal Buildings

2.29 Energy Used for Space Heating Per Floor Area Per Degree Day

3.1 Thermal Deficiencies Observed in Each Test Building

5.1 Comparison of Thermal Resistance Measured by Spot Radiometer with

Design Values in the Huron Building

5.2 Comparison of Thermal Resistance Measured by Spot Radiometer with

Design Values in the Ann Arbor Building

6.1 Tracer Gas Sampling Locations

6.2 Average Air Infiltration Rates of Each Federal Building

6.3 Typical One-Hour Decay Test for Anchorage

6.4 Typical One-Hour Decay Test for Springfield

6.5 Typical One-Hour Decay Test for Norfolk

6.6 Typical One-Hour Decay Test for Huron

6.7 Typical One-Hour Decay Test for Columbia

6.8 Data Files for Ann Arbor Building with No Outside Air Intake

6.9 Data Files for Ann Arbor Building with Outside Air Intake

XV 11
6.10

6.11

6.12

6.13

6.14

6.15

6.16

6.17

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Anchorage, AK

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Columbia, SC

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Norfolk, VA

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Springfield, MA

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Pittsfield, MA

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Huron, SD

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Fayetteville, AR

Average Air Exchange Rates in Various Temperature Bins During

Unoccupied Periods with Dampers Closed - Ann Arbor, MI

6.18

Average Ventilation Rates in the Buildings

6.19

Recommended Minimum Ventilation Rates in the Buildings

6.20

Monthly Average Ventilation Rates

7.1 Curve Fits to Pressurization Data and Pressure Measurement Range

7.2 Pressurization Test Results in Terms of 0.1 in H2O Flow Rates

7.3 Results of Window Pressurization Tests

7.4 Fraction of Total Building Leakage Associated with Windows

7.5

Predictions of the Shaw-Tamura Large Building Model

8.1 Construction Details of Building Components in Test Buildings

8.2 Comparison of Wall Thermal Resistances Measured with a Portable

Calorimeter and Heat Flow Meters to Corresponding Design Values

9.1 Details of Building Components in Thermal Bridge Measurements

9.2 Measured Heat Flow Rates and Thermal Resistance Values of Building

Components in Thermal Bridge Analysis

9.3 Estimates of the Heat Losses Resulting from Thermal Bridges

Estimate of Above Grade Design Heat Losses

xviii

10.1
10.2 Comparison of Energy Consumed for Space Heating Versus Transmission

Losses

xix

1 . INTRODUCTION

The federal government presently owns and leases thousands of buildings

throughout the United States. The General Services Administration (GSA)

constructs new buildings each year, some of which have thermal defects in

the building envelopes due to either poor workmanship or a misunderstanding

of the construction specifications. A strong need exists for viable, in

situ and nondestructive survey techniques to verify the thermal integrity

of the envelope systems of office buildings under construction. In this

way, thermal defects can be identified and located, and the contractor can carry out remedial action prior to departure from the construction site.

All buildings degrade with age and require periodic maintenance. The

potential causes of serious deterioration in the building often produce

thermal anomalies long before serious damage has occurred. The detection

of these anomalies can lead to corrective action before more costly repairs

are required. Areas where thermal anomalies occur can also lead to poor

thermal comfort and cause adverse reactions from the building occupants.

In order to develop a diagnostic program for assessing the thermal

performance of federal office buildings, GSA and NBS developed a two-phase

project to identify and assess existing measurement methods which could be

implemented by GSA using either government employees or private sector

contractors

Phase I

In phase I, a technical report entitled "Measurement Methods for Evaluation

of Thermal Integrity of Building Envelopes", NBSIR 82-2605 was prepared

[1]. This report reviewed the technical methods which could be used to assess the integrity of the exterior envelopes of Federal buildings. The

inspection techniques considered were: ground-based infrared thermographic

surveys, aerial infrared surveys; tracer gas air infiltration measurement;

pressurization tests for measuring building envelope tightness; and spot

radiometer measurements (both the temperature measuring and radiositymeasuring types) for detecting gross defects. Heat flow meters, a portable

calorimeter and an envelope thermal testing unit developed by Lawrence

Berkeley Laboratories were also considered for determining the thermal

characteristics of the envelope.

The techniques described in the phase I report could be used to find,

locate and assess the heat loss resulting from the following deficiencies:

1) uninsulated walls

2) uninsulated ceilings/roofs

3) partially insulated areas

4) air leakage

5) heat loss at joints

6) thermal by-passes

7) below-grade heat loss

8) thermal bridges

9) wet insulation

10) shrinkage in foam insulation

11) settling of loose-fill insulation

12) air movement around vapor barriers

1
In addition to locating deficiencies, the techniques could be used to

quantify heat losses, to determine the extent of deterioration, and to

suggest remedial action. They are applicable to both new and existing

buildings, although the manner in which they are applied will differ.

A common presentation format was adopted to describe the required method,

equipment and instrumentation; wherever applicable the information was

organized as follows:

Summary

Description of Equipment

Theory

Guidelines for Conducting Measurements

Interpretation of Results

Accuracy of Techniques

Availability of Equipment and Services

Previous Usage

Personnel Training Requirements

Program Application Restrictions

Phase II

The methods described in the phase I first report had not previously been

applied systematically to office buildings. Phase II was designed to

assess the usefulness of various diagnostic procedures described in the

phase I report by having the National Bureau of Standards perform a series

of the tests on eight Federal office buildings during the period from

September 1982 to August 1983. The buildings were located in Anchorage,

AK, Columbia, SC, Norfolk, VA, Springfield, MA, Pittsfield, MA, Huron, SD,

Ann Arbor, MI, and Fayetteville, AR. The tests which were performed on

these buildings consisted of: fan pressurization to assess the tightness

of the building envelope, tracer gas measurements of the natural air

infiltration rates and ventilation rates of the buildings, ground-based

infrared thermography, aerial thermography, inspection of the buildings

with spot radiometers, determination of the thermal conductance or U-value

using heat flow meters and a portable calorimeter, and leakage testing of

the components of the building. Table 1.1 gives a schedule of the tests

performed. A detailed technical description of these tests methods can be

found in the report of the first phase of this project [1].

It was originally intended to analyze the costs of the tests and

appropriate retrofit procedures and of the expected energy savings in order

to develop an economic evaluation of the benefits of the diagnostic

techniques. However, an insufficient amount of data was available. It

does not appear that such a diagnostic and retrofit approach is economical

in existing buildings due to the expense of repairs in existing buildings.

Such a diagnostic program probably makes sense in new buildings before they are finished-off and the contractor has left the site.

Chapter 2 of this report describes the eight federal office buildings

evaluated. The data presented in this chapter include the building

dimensions, the designed thermal parameters of the building envelopes,

pertinent characteristics of the building HVAC systems and the energy used

in the fiscal year 1981.

2
Table 1.1 Schedule of Tests

Anchorage

Ann Arbor

Columbia

Fayetteville

Huron

Norfolk

Pittsfield

Springfield

nspection

Visit

Tracer Fan Component Ground Aerial Spot

Air Pressuri- Pressuri- Thermo- Thermo- Radiometei

Infiltration zation zat ion gjaphy eraohv Inspection

8-82 9-82 9-82 5-83 1-83 5-83

1-

83

5-83

4-82 10-82 10-82 5-83 2-83 - 3-83

2-

83

5-83

8-82 11-82 11-82 5-83 1-83 3-83

1-83 5-83

5-83

8-83

8-82 11-82 11-82 6-83 3-83

2-83

6-83

8-82 10-82 10-82 - 3-83

1-83

6-83

8-82 10-82 10-82 5-83 1-83

1-83

5-83

8-83

8-82 10-82 10-82 6-83 2-83

2-83

6-83

8-82 11-82 11-82 - 2-83 3-83

2-83

6-83

Thermal

U-Value

5-83

2-83

2-

83

3-

83

2-

83

3-

83

3-83

3
Chapter 3 describes the results of ground infrared thermographic inspection

of the buildings. Both interior and exterior thermographic inspections

were performed by NBS staff members. These inspections were performed

using both short wavelength (2-5 micron) and long wavelength (8-12 micron)

imaging systems. Sample thermograms for each building are given,

indicating the major deficiencies found. The thermographic data were

analyzed to produce a classification of the types of defects located and

the area of the exterior envelope affected by the defects.

Chapter 4 discusses the results of the aerial infrared thermographic

inspections performed by private contractors on three of the large office

buildings. The purpose of the aerial infrared inspections were to assess

the integrity of the building roofs. Two of the inspections were performed

using infrared imaging systems from helicopters, the third was performed

using a line scanner from a fixed wing aircraft. The two contractors who

used imaging systems also inspected the roofs by a walk-on procedure.

Chapter 5 presents the results of an audit of two small office buildings

performed by two private contractors using spot radiometers. These

contractors used the spot radiometers to estimate the thermal resistance

(R-value) of the building envelope. These results are compared with the

building specifications.

In Chapter 6 the results of the air infiltration and ventilation

measurements using a tracer gas are given. Sampling and injection tubing

were installed in the fall of 1982 and an automatic air infiltration

monitor previously designed by NBS was used to measure the air infiltration

and ventilation rates during each of the major climatic seasons (three

automated air infiltration systems were used on this project). The data

are analyzed to determine average air infiltration and ventilation rates

for the buildings, the weather dependence of the air infiltration and

ventilation rates, the minimum ventilation rates experienced by the

buildings and the influence of air infiltration on the building's thermal

performance

.

Chapter 7 describes the results of the building tightness tests using fan

pressurization. Whole building pressurization tests were performed on seven of the federal office buildings using the building HVAC fans. The

results of these tests are compared to the results of the air infiltration

tests using a tracer gas. The results of component pressurization tests

are also presented and the importance of windows on the tightness of the

building envelope is assessed. A comparison is made between predicted

infiltration rates, based on a model which uses the results of the building

tightness tests, and measured air infiltration rates.

Chapter 8 gives the results of the measurement of the thermal resistance of

the building envelopes. These tests were performed using both heat flow

meters and portable calorimeters and a micro-computer for recording the

data. Two such systems were deployed to measure the thermal resistance of

sections of the exterior envelope of seven of the buildings.

Chapter 9 gives a quantitative estimate of the importance of thermal

bridges on the performance of the building insulation system. Thermal

bridges were detected in four of the office buildings during the

thermographic inspection. An analysis of the thermographic data and the

4
results of heat flow meter tests are used to calculate the increase in heat

flow due to the thermal bridging.

Chapter 10 presents a summary of the results of the diagnostic tests. A

comparison is made between the results of the diagnostic tests and the

energy used by the buildings.

This report contains three appendices. In Appendix A, a methodology is

presented for assessing the economics of diagnostic measurements.

Appendices B and C give the specifications used by NBS for procuring the

services of private contractors for performing audits using spot

radiometers and aerial infrared thermographic inspections. These serve as models of specifications for procuring the services of private contractors

for the other measurement methods.

5
2. Building Descriptions

The eight federal office buildings are located in the cities shown in the

map in figure 2.1. In general these are new buildings (less than three

years old), designed to the GSA energy guidelines of less than 55,000

Btu/ft 2 (630 MJ/m ) per year of on-site energy and less than 100,000

Btu/ft 2 (1,100 MJ/mZ

) per year of off-site energy. The building in

Fayetteville, AR is about ten years old and was built before these energy

guidelines for new federal office buildings were in effect. Though these

buildings tend to perform better than most existing federal office

buildings, none has met the energy guidelines during its first few years of

occupancy. However, the guidelines were not intended for energy use

prediction, but to influence the design process. In addition, the

guideline makes no distinction between the actual building and a generic

building with features including ten hour a day, five day a week occupancy, no food service, no computer space and no site lighting.

For the purpose of this study the buildings in Anchorage, AK; Springfield,

MA; Norfolk, VA; and Columbia, SC are considered large office buildings

(over 100,000 ft 2 (92,900 m

2

) of occupiable floor area). Columbia is 15

stories high, Norfolk 8 stories. Anchorage between two and six depending

on the module, and Springfield five stories. The buildings in Pittsfield,

MA; Huron, SD; Ann Arbor, MI; and Fayetteville, AR are considered small

office buildings (less than 100,000 ft 2 (92,900 m

2

) of floor area). These

small office buildings range in height from two to five stories. Schematic

diagrams and a photograph of each building are given in figures 2.2 through

2.9.

All but two of the buildings have variable volume air handlers in the major

zones of the buildings. They are all heated by perimeter heating systems,

which are generally hydronic. The building in Columbia has two perimeter

heating systems. In the Norfolk building, heaters and air conditioners

have been added to the air system on floors which have proved difficult to

heat and cool. They all have central chiller systems for cooling the core spaces Of the buildings. The buildings in Anchorage and Springfield have

underground garages. The Norfolk building has an exterior garage. The

physical dimensions of the buildings are given in Table 2.1.

The characteristics of the exterior walls of the buildings are summarized

in Table 2.2. The buildings have masonry type construction of the wall

systems, though the manner in which the insulation was applied varied. All

of the buildings have insulating glass windows. Table 2.3 describes the

construction of the roof systems for each building. A summary of the

thermal properties of the building envelopes (above grade) is given for

each building in Tables 2.4 to 2.11. The effective design thermal

resistance R

g ££ of the walls varies from 17.2 F*ft 2 *hr/Btu (3.0 m

2,K/watt)

for the Anchorage federal building to 3.2 F*ft 2 *hr/Btu (0.6 m

2 *K/watt) for

the Fayetteville federal building. The effective design thermal resistance

of the roofs varies from 9.6 F’ft^’hr/Btu (1.7 m

2 *K/watt) for the Ann Arbor

federal building to 26.3 F*ft 2 *hr/Btu (4.6 m

2 *K/watt) for the Fayetteville

federal building. The total envelope conductive resistance varies from 3.5

F*ft 2 *hr/Btu (0.6 m

2 *K/watt) for the Fayetteville federal building to 9.4

F*ft 2 *hr/Btu (1.7 m

2 *K/Watt) for the Anchorage federal building.

6
Descriptions of the HVAC systems are given in Tables 2.10 to 2.19. The

mechanisms for controlling outside air intake vary among the eight

buildings. In most buildings, outside air intake is kept to a minimum when

the building is being heated or cooled in order to reduce the space

conditioning load. During mild weather, outside air is often used to cool

the building. The amount of outside air intake, and the times when outside

air intake is increased, are controlled by a variety of schemes. An

economizer control uses the outside temperature to determine when outside

air should be used for cooling. Enthalpy control uses indoor and outdoor

humidity levels in addition to temperature. The amount of outside air

intake for cooling is generally determined by a control system which

compares the discharge or return air temperature to some temperature

setting. The ventilation control strategies and the air handling systems

in each building are outlined below, along with other information on mechanical systems and the zoning of the buildings.

The Anchorage building is divided into six modules, (each with its own

ventilation system) which are connected by an open lobby/atrium and

communicate freely. Anchorage is the only building without return fans.

The mechanical systems are computer controlled and use a minimum of outside

air during the heating season. During warmer weather, outside air is used

to cool the building, with the outside air intake level determined by the

supply air temperature.

In Ann Arbor, the building's main mechanical system serves most of the

building with separate systems for the lobby and post office. The outside

air intake is based on the outside air temperature (an economizer), and the

amount of outside air intake is controlled by the return air temperature.

Columbia has a single mechanical system for floors two through fifteen and

separate systems for the lobby and the first floor/basement zones. The

mechanical system is controlled by a computer and uses an enthalpy

controller to determine outside air intake levels.

There are two fan systems on each of the five floors of the Fayetteville

building with an additional system for the courtroom on the fifth floor.

The outside air intake is controlled manually by the building operator.

The Huron building has two mechanical systems, one for the north zone and

another for the south zone. On each floor, the north and south zones are

open to each other. The outside air intake is based on enthalpy control.

Norfolk has one mechanical system for most of the building, and a smaller

system for the lobby area. The main HVAC system uses enthalpy control to

regulate the outside air intake.

The Pittsfield building has a separate fan system for each of its two

floors. The outside temperature is used to determine whether outside air can be used to cool the building.

There are three fan systems in the Springfield building, one each for the

north zone, the south zone and the lobby/atrium. The outside air dampers

are adjusted to maintain a supply air temperature of about 13°C (55°F)

during the entire year. Thus, outside air is used to condition the

7
building unless the outside temperature is below the supply air temperature

setting

.

Table 2.20 gives the average degree days for each site. These vary from

2567 F'Days (1426 C’Days) for Columbia, SC to 10,804 F’Days (6035 C’Days)

for Anchorage, AK. The fuel records for fiscal year 1981 are given in

Tables 2.21 to 2.27 for seven of the buildings. The Springfield federal

building had no previous fuel records since it was a new building. The

summer months are those with an insignificant amount of heating. Table

2.28 gives an estimate of the electrical base load and summer excess load

for each building (approximate air conditioning load). Note that the base

load contributed from 67% to 92% of the electric usage of the building,

while the air conditioning loads were from 5% to 23% of the electric usage.

Table 2.29 gives a summary of the energy used for space heating per floo^

area per degree day for each building. This varied from 2.6 Btu/F*day*f

t

z (0.35 KW/(K*m^)) for the Huron federal building to 11.9 Btu/F*day*f t^

(1.62 KW/(K*m^)) for the Ann Arbor federal building. The values in Table

2.29 give a relative measure of the energy performance of each building.

8
Table 2.1

Building Dimensions

Conditioned Volume Rentable Floor Area

ft3 ft z (mz

)

Anchorage 6,140,000 (174,000) 490,000 (45,500)

Ann Arbor 1,120,000 ( 31,700) 52,700 ( 4,900)

Columbia: Tower

Only

4,420,000 (125,000) 216,000 (20,100)

Total 5,610,000 (159,000) 266,000 (24,700)

Fayetteville 751,000 ( 21,300) 36,600 ( 3,400)

Huron 972,000 ( 27,500) 69,100 ( 6,420)

Norfolk 2,130,000 ( 60,300) 186,000 (17,300)

Pittsfield 301,000 ( 8,520) 18,600 ( 1,730)

Springfield 2,040,000 ( 57,700) 146,000 (13,500)

Total Floor Area Exterior Envelope Are

ft z (mz

) ft z (m^)

Anchorage 522,000 ( 48,500) 248,000 (23,000)

Ann Arbor 56,700 ( 5,270) 71,400 ( 6,630)

Columbia: Tower

Only

223,000 ( 20,700) 149,000 (13,800)

Total 286,000 ( 26,600) 213,000 (19,800)

Fayetteville 39,400 ( 3,600) 52,400 ( 4,830)

Huron 74,400 ( 6,910) 71,300 ( 6,620)

Norfolk 200,000 ( 18,600) 130,000 (12,100)

Pittsfield 20,000 ( 1,860) 24,800 ( 2,300)

Springfield 157,000 ( 14,600) 96,200 ( 8,940)

9
Table 2.2

Description of Typical Exterior Walls of Each Building

Building

Locat ion

No. of

Modules

No . of

Stories Typical Wall Construction

Anchorage 6 2-6 Precast concrete panel, semirigid glass fiber insulation

board, gypsum wallboard on metal studs.

Ann Arbor 1 4 Quarry tile, metal lath and

mortar bed, semi-rigid glass

fiber insulation board,

acoustic wall panel.

Columbia 2 2,15 Granite siding, concrete, glass

fiber blanket insulation, gypsum

wallboard.

Fayetteville 1 5 Face brick, concrete block.

Huron 1 4 Face brick, lightweight

concrete masonry unit, semirigid glass fiber insulation

board, gypsum wallboard.

Norfolk 1 8 Face brick, air space, gypsum

board sheathing, glass fiber

blanket insulation, gypsum

wallboard

.

Pittsfield 1 2 Face brick, semi-rigid glass

fiber insulation board, brick.

Springfield 1 5 Precast concrete panel, semirigid glass fiber insulation

board, gypsum wallboard on metal studs.

10
Table 2.3

Description of the Roof Insulation Systems

Anchorage - Protected membrane - concrete pavers, 3 in. (7.6 cm) rigid

foam insulation, membrane, 6 in. (15.2 cm) concrete.

Ann Arbor - Built-up roof membrane, 1-1/2 in. (3.8 cm) rigid insulation

on 1-1/2 in. (3.8 cm) x 20 ga. composite concrete and steel

deck.

Columbia - Built-up roof membrane 2 in. (5.1 cm) rigid insulation, 3

in. (7.6 cm) lightweight concrete, 6 in. (15.2 cm)

structural concrete.

Fayetteville - Built-up roof membrane 4 in. (10.2 cm) lightweight

insulating concrete, 2 in. (5.1 cm) insulation board.

Huron - Built-up roof membrane 3 in. (7.6 cm) rigid insulation, 2 in. (5.1 cm) concrete.

Norfolk Built-up roof membrane 4 in. (10.2 cm) built-up roof

membrane, 1/2 in. (1.3 cm) plywood, 2 in. (5.1 cm) rigid

insulation, 5-1/2 in. (14.0 cm) concrete slab on steel roof

deck

.

Pittsfield - Built-up roof membrane 3/4 in. (1.9 cm) built-up roof

membrane, 2-1/2 in. (6.4 cm) rigid insulation (R-20),

concrete slab on 1-1/2 in. (3.8 cm) x 20 ga. steel deck.

Springfield - Built-up roof membrane, rigid insulation (R-14), metal deck.

11
Table 2.4

Thermal Characteristics of Building Envelope

for Anchorage, AK Federal Building

Effective Resistance

Design R

Area Transmission Loss eff

ft 2 (m2

) Btu/F *hr (W/K) F *f

t

2 *hr/Btu (m2 *K/W

)

Opaque Wall 98,932 ( 9,191) 5,736 ( 3,023) 17.2 (3.0)

Glass 35,154 ( 3,266) 14,648 ( 7,719) 2.4 (0.4)

Roof 112.228 (10.426) 5.754 ( 3.032) 19.5 (3.4)

Total 246,314 (22,883) 26,138 (13,775) 9.4 (1.7)

Table 2.5

Thermal Characteristics of Building Envelope for

Ann Arbor, MI Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F ‘hr (W/K) F *f

t

2 *hr/Btu (m2 -K/W)

Opaque Wall 26,776 ( 2,487) 5,424 ( 2,858) 4.9 (0.9)

Glass 14,487 ( 1,346) 7,968 ( 4,199) 1.8 (0.3)

Roof 24.062 ( 2.235) 2.499 ( 1.317) 9.6 (1.7)

Total 65,325 ( 6,069) 15,891 ( 8,375) 4.1 (0.7)

12
Table 2.6

Thermal Characteristics of Building Envelope for

Columbia, SC Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

CN

4J 4-1 (m2

) Btu/F *hr (W/K) F*ft 2, hr/Btu (m2 'K/W

)

Tower

Opaque Wall 103,412 ( 9,607) 8,667 ( 4,568) 11.9 (2.1)

Glass 16,091 ( 1,494) 15,527 ( 8,183) 1.0 (0.2)

Roof 23.336 ( 2.168) 1.553 ( 818) 15.2 (2.7)

Total 142,839 (13,270) 25,747 (13,569) 5.5 (1.0)

Courthouse

Opaque Wall 22,478 ( 2,088) 3,313 ( 1,746) 6.8 (1.2)

Glass 6,132 ( 570) 5,917 ( 3,118) 1.0 (0.2)

Roof 35.455 ( 3.294) 2.832 ( 1.492) 12.5 (2.2)

Total 64,065 ( 5,952) 12,062 ( 6,356) 5.3 (0.9)

Volume

Tower 4.42 x 10 6 ft 3 (1.25 x 10 5 m

3

) Courthouse 1.19 x 10 6 ft 3 (3.36 x 104 m

3

)

Table 2.7

Thermal Characteristics of Building Envelope for

Fayetteville, AR Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F ’hr (W/K) F *f

t

2 *hr/Btu (m2 ’K/W )

Opaque Wall 29,737 ( 2,763) 9,306 ( 4,904) 3.2 (0.6)

Glass 8,837 ( 821) 4,684 ( 2,468) 1.9 (0.3)

Roof 13.402 ( 1.245) 509 ( 268) 26.3 (4.6)

Total 51,976 ( 4,829) 14,499 ( 7,641) 3.5 (0.6)

13
Table 2.8

Thermal Characteristics of Building Envelope for

Huron, SD Federal Building

Area

Design

Transmiss ionl Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F’hr (W/K) F •ft 2 *hr/Btu (m2 *K/W)

Opaque wall 36,003 ( 3,344) 3,071 ( 1,618) 11.7 (2.1)

Glass 4,853 ( 451) 1,990 ( 1,048) 2.4 (0.4)

Roof 20.989 ( 1.950) 1.733 ( 388) 12.1 (2.1)

Total 61,845 ( 5,745) 6,794 ( 3,580) 9.1 (1.6)

Table 2 .9

Thermal Characterises of Building Envelope for

Norfolk, VA Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F ‘hr (W/K) F •ft 2 *hr/Btu (m2 *K/W)

Opaque Wall 83,173 ( 7,726) 6,099 ( 3,214) 13.6 (2.4)

Glass 17,948 ( 1,667) 9,692 ( 5,108) 1.9 (0.3)

Roof 32,272 ( 2.998) 2.259 L 1.190) 14.3 (2.5)

Total 133,393 (12,392) 18,050 ( 9,512) 7.4 (1.3)
Table 2.10

Thermal Characteristics of Building Envelope for

Pittsfield, MA Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F *hr (W/K) F

, ft 2, hr/Btu (m2 *K/W

)

Opaque Wall 10,596 ( 984) 1,052 ( 554) 10.0 (1.8)

Glass 1,760 ( 164) 915 ( 482) 1.9 (0.3)

Roof 12.444 ( 1.156) 1.032 ( 544) 12.0 (2.1)

Total 24,800 ( 2,304) 2,999 ( 1,580) 8.3 (1.5)

Table 2.11

Thermal Characteristics of Building Envelope for

Springfield, MA Federal Building

Area

Design

Transmission Loss

Effective Resistance

R

eff

ft 2 (m2

) Btu/F *hr (W/K) F *ft 2 *hr/Btu (m2 *K/W

)

Opaque Wall 50,203 ( 4,664) 4,292 ( 2,261) 11.7 (2.1)

Glass 18,762 ( 1,743) 9,117 ( 4,805) 2.1 (0.4)

Roof 25.784 L 2.395) 1.865' ( 982) 13.8 (2-4)

Total 94,749 ( 8,802 15,274 ( 8,049) 6.2 (1.1)

15
Table 2.12

Air Handler Characteristics of HVAC System for

Anchorage, AK Federal Building

Fan Capacitv Vo lume Served

cfm (nr/s) ft 3 (nr) Type

Module A 31,500 (14.8) 567,000 (16,046) VAV

Module B 32,800 (15.4) 661,000 (18,706) VAV

Module C 63,000 (29.6) 1,108,000 (31,356) VAV

Module D 51,600 (24.25) 987,000 (27,932) VAV

Module E 50,100 (23.5) 1,100,000 (32,715) VAV

Module F 61,200 (28.8) 1,100,000 (31,130) VAV

VAV - variable volume system

Table 2.13

Air Handler Characteristics of HVAC System for

Ann Arbor, MI Federal Building

Fan Capacitv Volume Served

cfm (m /s) ft 3 (m3

) Type

Floors 1 to 4

except Mail Room

56,000 (15.3) 919,000 (26,007) VAV

Mail Room 8,300 (3.9) 153,900 (4,355) CV

Lobby 4,050 (2.3) 47,900 (1,356) CV

VAV - variable volume

CV - constant volume

16
Table 2.14

Air Handler Characteristics of HVAC System for

Columbia, SC Federal Building

Fan Capacity

cfm (m /s)

Tower Core

#1 106,000 (49.8)

#2 106,000 (49.8)

Tower Perimeter

West 10,200 (4.8)

North, South,

East 33,700 (15.8)

1st Floor &

Basement 20,000 (9.4)

1st Floor Lobby 8,000 (3.8)

Courthouse 75,000 (35.3)

Courthouse Lobby 10,000 (4.7)

VAV - variable volume system

CV - constant volume system

Vo lume Served

ft 3 (nr) Type

2,575,000 (72,873)

VAV

VAV

209,000 (5,915) VAV

645,000 (18,254) VAV

347,000 (9,820) VAV

71,104 (2,012) CV

1,039,000 (29,404) VAV

76,000 (2,151) CV

17
Table 2.15

Air Handler Characteristics of HVAC System for

Fayetteville, AR Federal Building

Fan Capacity Volume Served

cfm (m /s) ft 3 (nr) Type

1st Floor North 8,450 (4.0) 64,934 (1,838) CV

1st Floor South 7,271 (3.4) 52,520 (1,486) CV

2nd Floor North 5,290 (2.5) 63,984 (1,811) CV

2st Floor South 6,278 (3.0) 63,607 (1,800) CV

3rd Floor North 5,290 (2.5) 63,984 (1,811) CV

3rd Floor South 6,278 (3.0) 63,607 (1,800) CV

4th Floor North 4,818 (2.3) 61,956 (1,753) CV

4th Floor South 5,750 (2.7) 64,237 (1,818) CV

5th Floor North 6,648 (3.1) 81,018 (2,293) CV

5th Floor South 9,515 (4.0) 93,582 (2,658) CV

5th Floor Courtroom

CV - constant volume

4,200 (2.0

system

46,791 (1,324) CV

Table 2.16

Air Handler Characteristics of HVAC for

Huron, SD Federal Building

Fan Capacity Volume Served

cfm (m3 /s) ft 3 (m3

) Type

Zone 1 (North) 23,970 (11.3) 463,000 (13,103) VAV

Zone 2 (East) 26,200 (12.3) 507,000 (14,348) VAV

VAV - variable volume system

18
Table 2.17

Air Handler Characteristics of HVAC System for

Norfolk, VA Federal Building

Fan Capacitv Volume Served

cfm (nr/s) ft3 (nr) Type

Floor 2 through 8 76,450 (35.9) 1,864,000 (52,751) VAV

1st Floor 266,250 (7,535) CV

Note: Heat two electric boilers 300 KW each

Added 50 heaters to floors 1 through 4

Two chillers 200 tons and 125 tons

Table 2.18

Air Handler Characteristics of HVAC System for

Pittsfield, MA Federal Building

Fan Capacitv

cfm (nr/s)

Volume Served

ft 3 (m5

) Type

1st Floor 6,900 (3.2) 154,295 (4,367) VAV

2nd Floor 8,950 (4.2) 146,655 (4,150) VAV

Table 2.19

Air Handler Characteristics of HVAC System for

Springfield, HA Federal Building

Fan Capacitv

cfm (mJ /s)

Volume Served

ftMm3

) Type

North Zone 56,650 (2.6) 778,000 (22,018) VAV

South Zone 35,650 (16.8) 495,000 (14,009) VAV

Atrium 6,600 (3.1) 133,000 (3,764) CV

VAV - variable volume system

CV - constant volume system

19
Table 2.20

Degree Days for Building Sites - Base 65°F (18.3°C)

Degree Day - °F (°C)

Anchorage, AK 10,864 (6,035)

Ann Arbor, MI 6,293 (3,496)

Columbia, SC 2,567 (1,426)

Fayetteville, AR 3,292 (1,829)

Huron , SD 8,223 (4,568)

Norfolk, VA 3,421 (1,901)

Springfield, MA 7,273 (4,041)

Pittsfield, MA 7,578 (4,210)

Table 2.21

Power and Fuel Records for Federal Building in

Anchorage, AK for FY1981

Electricity Demand Gas

KWH KW cubic feet

January 795,200 0 2,170,200

February 596,000 0 2,292,300

March 621,600 0 1,709,900

April 690,400 0 1,347,400

May 610,400 0 280,500

June 683,200+ 0 0

July 715,200+ 0 0

August 718,400+ 0 0

September 718,400+ 0 395,000

October 615,200 0 711,400

November 624,000 0 1,842,800

December 719.200 0 4.410.200

8,107,200 0 15,159,200

+ Summer months

20
Table 2.22

Power and Fuel Records for Federal Building in

Ann Arbor for FY1981

Electricity Demand Gas

KWH KW cubic feet

January 97,380 189 631,000

February 91,280 194 591,500

March 89,520 192 385,000

April 95,180 187 282,200

May 85,160 237 28,700

June + 119,500 284 25,300

July + 145,240 282 22,900

August + 128,480 292 8,400

September + 126,880 278 106,300

October 89,160 230 417,900

November 82,360 188 591,700

December 82.680 299 858.200 *

1,232,820 2,852 3,949,100

* Corrected

+ Summer months

Table 2.23

Power and Fuel Records for Federal Building in

Columbia, SC for FY1981

Electricity Demand Oil

KWH KW Gallon

January 396,000 1,204 _ February 342,000 1,204 - March 355,500 1,296 - April 387,000 + 1,804 - May 454,400 + 1,841 - June 523,500 + 1,906 - July 786,000 + 1,836 - August 639,000 + 2,221 - September 547,500 + 2,269 - October 463,500 + 1,777 — November 378,000 1,679 - December 363.000 1,193 -

5,635,500 20,230 19,101 *

* Total FY1981 yearly delivery (oil delivered in 8,000 gallon lots)

.

+ Summer months

21
Table 2.24

Power and Fuel Records for Federal Building in

Fayetteville, AR for FY1981

Electricity Demand Gas

KWH KW cubic feet

January 42,840 324 307,000

February 34,200 194 232,000

March 36,180 248 153,000

April 44,100 216 10,000

May + 43,740 227 13,000

June + 54,540 227 6,000

July + 64,980 232 6,000

August + 62,820 227 5,000

September + 49,140 226 5,000

October 38,880 203 34,000

November 36,880 185 154,000

December 39.060 118 296.000

549,360 2,627 1,221,000

+ Summer months

Table 2.25

Power and Fuel Records for Federal Building in

Huron, SD for FY1981

Electricity* Demand Gas* (Oil)

KWH KW cubic feet (Gallons)

January 60,120 206 431,800

February 68,100 254 400,000

March 53,350 220 213,600

April 55,680 225 157,400

May 53,760 224 11,200 (193)

June + 62,880 308 0

July + 61,440 355 0

August + 70,080 342 0

September + 59,040 303 0

October 55,200 333 3,600

November 59,820 204 78,200

December 53.640 212 190.800

713,340 3,186 1,486,600

+ Summer Months

* Electricity 1981 789,100 cubic feet

Gas 1982 Fuel 1981 2,069 gallons oil

22
Table 2.26

Power and Fuel Records for Federal Building in

Norfolk, VA for FY1981

Excess Over

Electricity Demand Base

KWH KW KWH

January 324,480 858 176,646

February 266,880 708 119,040

March 213,120 794 65,280

April 200,000 790 52,160

May + 148,000 650 160

June + 170,000 700 22,160

July + 236,160 596 88,320

August + 213,120 612 65,280

September + 203,520 550 55,680

October 147,840 646 0

November 192,000 920 44,160

December 268.000 988* 120.160

2,583,920 8,812 831,000

* December 1980

Excess Winter 577,000 KWH

Excess Summer 254,000 KWH

+ Summer Months

Table 2.27

Power and Fuel Records for Federal Building in

Pittsfield, MA for FY1981

Electricity Demand Oil

KWH KW Gallon

January 12,480 50 1,400

February 12,400 56 1,000

March 13,000 52 900

April 11,760 62 750

May 12,560 65 250

June + 11,440 70 0

July + 11,440 66 0

August + 12,240 68 0

September 11,280 42 100

October 12,800 46 250

November 12,880 46 900

December 13.040 49 1,175

147,320 672 6,725

+ Summer months

23
Table 2.28

Base and Excess Electrical Loads for

the Federal Buildings

(% of Summer (% of Winter (% of

Base Total Excess Total Excess Total

KWH/Month Usage) KWH Usage) KWH Usage)

Anchorage 610,400 (90%) 393,600 (5%) -

Ann Arbor 82,360 (80%) 190,660 (15%) -

Co lumb ia 355,500 (76%) 1,342,500 (23%) -

Fayetteville 36,180 (79%) 94,320 (17%) -

Huron 53,760 (90%) 59,445 (8%) -

Norfolk 147,840 (69%) 254,000 (10%) 577,000 (22%)

Pittsfield 11,280 (92%) 1,280 (1%) -

Table 2.29

Energy Used for Space Heating Per

Per Degree Day

Floor Area

Btu/(F*day*ft 2

) KW/ (K *m2)

Anchorage 2.9 0.40

Ann Arbor 11.9 1.62

Columbia 7.8 1.06

Fayetteville 10.1 1.38

Huron 2.6 0.35

Norfolk 4.2 0.57

Pittsfield 6.7 0.91

24
Figure 2.1 Location of the Eight Federal Office Buildings

ANCHORAGE FEDERAL BUILDING

Schematic of Overhead view

Figure 2.2 Schematic Diagram and Photograph of Federal

Building in Anchorage, AK

25
ANN ARBOR FEDERAL BUILDING

Schematic of First Floor

ANN ARBOR FEDERAL BUILDING

Schematic of East Elevation

Main return a 4tb Floor A

* Sample locations

3rd Floor A

Post Offico A Lobby

Figure 2.3 Schematic Diagram and Photograph of Federal

Building in Ann Arbor, MI

26
COLUMBIA FEDERAL BUILDING

Schematic off East Elevation

Mali * ratara

A

A

A

A

A

A

* Lobby

1st Floor/Basement Fan

13th Flaar

11th Flaar

9th Floor

7th Floor

6th Floor

3rd Floor £

A Sampla loeationa

a Courthouso

Fan

COLUMBIA FEDERAL BUILDING

Schematic of Overhead View

Figure 2.4 Schematic Diagram and Photograph of Federal

Building in Columbia, SC

27
FAYETTEVILLE FEDERAL BUILDING

Schematic of North Elevation

Schematic of First Floor

Nartb

1

Macbaaical

roeai Cerrider

Rear

labby

Fraat

labby Elavatara

Machaaical

raaai

Schematic of Fifth Floor

Figure 2.5 Schematic Diagram and Photograph of Federal

Building in Fayetteville, AR

28
HURON FEDERAL BUILDING

Schematic of East-West Building Section

* Sampla loeatloas

"North” Wing

Mechanical Panthouse

North return East return A A "East" Wing

3rd Floor north a * 3rd Floor east

2nd Floor north a * 2nd Floor east

1st Floor north A a 1st Floor east

HURON FEDERAL BUILDING

Schematic of Overhead View

North Wing

East Wing

Schematic Diagram and Photograph of Federal

Building in Huron, SD

29
NORFOLK FEDERAL RUILDING

Schematic of West Elevation

a Staple location

NORFOLK FEDERAL BUILDING

Schematic of North Elevation

Figure 2.7 Schematic Diagram and Photograph of Federal

Building in Norfolk, VA

30
PITTSFIELD FEDERAL BUILDING

Schematic of West Elevation

* Sample locations

PITTSFIELD FEDERAL BUILDING

Schematic of Overhead View

North

Corridor

Elevator

Figure 2.8 Schematic Diagram and Photograph of Federal

Building in Pittsfield, MA

31
SPRINGFIELD FEDERAL BUILDING

Schematic of South Elevation

* Simple licatii* Oitllai of Atria*

Saath iiaa

ratara Mochaaical

A A Poathoasa

North zoaa

ratara

A Sth Floor aarth

4th Flaar saath SOUTH NORTH

A 4th Floor aorth

ZONE i ^

z.« A

3rd Floar north

2ad Floor soath

A A 2nd Floor north

A

1st Floor north

SPRINGFIELD FEDERAL BUILDING

Schematic of First Floor

Figure 2.9 Schematic Diagram and Photograph of Federal

Building in Springfield, MA

32
3. Ground Infrared Thermographic Inspections

3.1 Background

Thermographic inspection with infrared (IR) imaging systems is a diagnostic

tool to locate thermal defects in a building envelope. IR thermography

employs non-contact scanning devices to convert the IR radiation from the

object surface to visible light by providing an image of the surface

intensity variation. The application of IR thermographic surveys to detect

thermal anomalies and to determine insulation effectiveness in large

buildings permits the selection of retrofit actions to be carried out to

achieve energy conservation. During field measurements, IR thermographic

inspections are usually carried out both internally and externally under

suitable weather conditions. Thermographic data can be collected by

photographing the thermal image display of the thermographic sensing system

or by recording the video output of the system directly for subsequent

reproduction. Information such as the temperature range of the sensing

system and the environmental conditions during inspection are also required

in addition to the thermographic data. A copy of such a thermal image,

which corresponds to the apparent radiance temperature distribution along

the surface, is called a thermogram. A typical thermogram of a surface

will provide an intensity-modulated image where the bright and dark

portions represent the hot and cold regions, respectively, and the grey

shades show intermediate ranges. Accordingly, the thermal integrity of the

buildings can be analyzed and interpreted from the thermograms and other

documentation

.

3.2 Summary of Results

Thermographic surveys were conducted during the heating season of 1982-83

at all eight federal buildings. Since these are all large buildings, they

were inspected thoroughly by exterior surveys with interior surveys only at some regions where thermal anomalies were detected or suspected by outside

inspections. A summary of thermal deficiencies interpreted from the

thermographic inspection for all eight buildings is given in table 3.1.

Note that the numerical calculations of the total wall area and percentage

of wall area subject to thermal defects in table 3.1 exclude the glass and

window areas of the outside surfaces. As indicated in table 3.1, the most

severe thermal defects that occur in these buildings, besides defects in

insulation, are air leakage through joints (wal 1-to-val 1 , cei ling-to-wa 1 1

,

and f 1 oor-to-wa 1 1 ) and window seals. Other common heat loss locations

observed include shrinkage of insulation, and air penetration paths in

walls and ceilings. The percentage of wall area subject to thermal defects

in these buildings was found to be between 6 and 18 percent, also given in

table 3.1. Descriptions of the envelope thermal integrity and examples of

defects observed in the thermograms are included in the following

discussion.

33
Table 3.1 Thermal Deficiencies Observed in Each Test Building

City ANCHR ANNAR COLUM FAYET HURON NORFK PITFD SPRFD

Total Wall

Area ft^ 81,800 9,700 113,900 15,900 38,300 66,400 10,900 47,300

(m2

) 7,600 904 10,580 1,480 3,560 6,170 1,010 4,390

Defective

Wajl Area 15,120 1,710 19,530 950 3,530 11,490 2,010 3,260

(m2

) 1,405 159 1,814 88 328 1,067 187 303

% of Wall Area

Subject to

Thermal Defects

18 18 17 6 9 17 18 7

Defects Observed:

Walls

Lack of

Insulation

Shrinkage or

* * * * *

Figures in

Insulation

* * * * * *

Cross Braces * * * Air Penetration * * * * * * *

Ceilings

Interior

Indentation

* * * * *

or Overhang * * * * *

Doors *

Windows * * * * * * * *

Seam Leakage

Wall-Wall * * * Floor-Wall * * * * * Wall-Panels * * * *

Basement *

Pipe or Duct * *

Thermal Bridges * * * * *

34
3.2.1 Description of Thermal Defects in the Anchorage Federal Building

The federal building in Anchorage, AK is rather uniform in its thermal

anomalies, for the defects in the modules are consistent and regular and

the modules are nearly identical to one another, discounting the

differences in the number of floors. The major defects are the thermal

bridging at the panel supports and the leakage that occurs at the seams of

the interlocking panels, especially at the corners and along the edges of

the adjoining mirror walls, as illustrated in the thermograms from figures

3.1 and 3.2. The mirror walls in figure 3.2 appear as bands of light and

dark, with the light bands having one-way mirrors for the floors inside and

the dark bands having walls behind them. The high rating, 18%, of wall

area exposed to thermal defects is primarily due to this corner leakage and

thermal bridging at the structural supports of the panels. Examples are the SW corner of the A module in figure 3.2-2 and the vertical seams in

figures 3.2-3 and 3.2-4. (The bright spot in the center of figure 3.2-3 is

the heat from a streetlight.) There also is extensive heat loss from the

first floor windows that are on every module as illustrated by the west

face of the A module in figure 3.2-4.

Mirror wall section

Seam leakage at panel joints

Figure 3.1 Sample Defects Observed in the Anchorage Federal Building

35
Figure 3.2 Thermal Defects Observed in the Anchorage Building

3.2-1

Mirror wall section

3.2-2

SW corner of

A module

3.2-3

SE corner of E wall,

upper floor F module

3.2-4

West face of the

A module

36
3.2.2 Description of Thermal Defects Observed in the Ann Arbor Federal

Building

The federal building in Ann Arbor has many types of thermal anomalies, but

the predominant defect is the lack of insulation in large rectangular

sections in the east and west walls. Note the large heat loss areas in

figures 3.3, 3.4. There are similar voids in the insulation in the wall

outcroppings that face east in the top center of the building as seen in

figure 3.4-6. Leakage in the seams is also a distinct problem in the

building, as is evident in the thermograms of the adjoining panels in

figures 3.4-1 and 3.4-2. The wall-floor joints are sources of heat loss as well and are found in nearly all exterior wall areas. The strong flaring

in the close-up of the east wall at the south end, shown in figure 3.4-3,

is indicative of serious thermal defects due to air leakage in the top

seams. Note the cross-brace in the thermogram of the Post Office in figure

3.4-5 and some incompletely or unevenly insulated walls in figures 3.4-2

and 3.4-6, which the irregular voids indicate.

Rectangular wall area

Missing insulation

Figure 3.3 Sample Defects Observed in the Ann Arbor Federal Building

37
Figure 3.4 Thermal Defects Observed in the Ann Arbor Building

3.4-1

Middle two floors

of SW corner

3.4-3

E wall at the

S end

3.4-5

E wall at the N

end, first floor

Post Office

3.4-2

Top floors of the

W wall at the S end

3.4-4

E wall at the

S end

3.4-6

N face above and to

the left of the front

entrance

38
3.2.3 Description of Thermal Defects in the Columbia Federal Building

The thermal anomalies observed in the federal building in Columbia, SC

consists primarily of leakage through defects in the window panels and

voids in the insulation at the panel seams (figures 3.5 and 3.6). The

thermograms shown in figures 3.6-1 and 3.6-2 made by interior inspections

illustrate some of the thermal defects, such as poor insulation, missing

insulation, and compression of insulation around the window areas of this

building. Figures 3.6-3 and 3.6-4 indicate the compression and voids in

the insulation in the north wall of the fourth floor by interior and

exterior thermograms, respectively. Similar defects over the entire

building are the main contributors to the high percentage, 17% of wall area subjected to thermal anomalies. Note the seam leakage in the panels that

make up the solid edges in figure 3.6-4. The heat loss depicted in figure

3.6-5, which rises up the west edge of the south wall and across the top

edge of the building, is due to the perimeter zone HVAC system ducts.

The thermal integrity of the courthouse adjacent to the tower is also

imperfect. Figure 3.6-6 shows the leakage that occurs at the NW corner

indent of the courthouse, which is typical of the leakage at those seams.

Defective insulation or floor leakage

Window seams leakage

Figure 3.5 Sample Defects Observed in the Columbia Federal Building

39
Figure 3.6 Thermal Defects Observed in the Columbia Building

3.6-1

N wall on the fourth

floor of the tower

(interior)

3.6-3

SE corner of the

fourth floor

of the tower (interior)

k « T In ^

jte I

r vcTTr

si -

C

3.6-2

N wall on the fourth

floor of the tower

(interior)

3.6-4

Lower west face of the

tower at the N end

3.6-5

S face of W end

40

3.6-6

NW corner indent of the

courthouse
3.2.4 Description of Thermal Defects Observed in the Fayetteville Federal

Building

Of all the federal buildings inspected, the wall areas of the Fayetteville

building are observed to be relatively uniformly insulated, however, this

is actually due to a lack of insulation in the exterior wall envelope

(figure 3.7 and 3.8). This indicates the limitation placed on infrared

methods when applied to uninsulated walls. The leakage of the wall-floor

seams are the predominant defects. Examples are the seams of the elevator

towers as shown in figures 3.8-1 and 3.8-2. This type of thermal defect is

also evident in the east and west walls below the overhangs where the roof

of the overhanging section appears to be a source of heat loss as seen by

the flaring against the tower in figure 3.8-1. Note that the heat loss

through the floor of the overhangs could be due to the corner seams, for

the defect is well-defined along the edges of the overhanging floor. There

are relatively few insulation voids which helps account for the low, 6%,

thermal defects of the total wall area.

Elevator towers at overhang area

Leakage in seams

between floors and

between walls

Figure 3.7 Sample Defects Observed in the Fayetteville Building

41
Figure 3.8 Thermal Defects Observed in the Fayetteville Building

3.8-1

NE corner with one

east face tower

3.8-2

NW corner with west

wall under overhang

3.8-3

E end with three

elevator towers

42

3.8-4

NW corner above N entrance

with view up to overhang
3.2.5 Description of Thermal Defects Observed in the Huron Federal

Building

The federal building in Huron, SD is relatively sound with respect to

thermal integrity (figures 3.9 and 3.10). The 9% thermal defects in wall

area are primarily due to leakage through seams between floors and thermal

bridges at intersections of walls, floors, and beams, as seen in figure

3.10-3. There is also flaring around and above the windows shown in

figures 3.10-1 and 3.10-3. Note how the seams appear to be more defective

as they approach the windows, especially as seen in figure 3.10-3. The

brightness in the leftmost side of figure 3.10-4 is due to the windows near

the front entrance in the background. Figure 3.10-4 is an interior

thermogram of the fourth floor indicating a beam which conducts cold air in on the right hand side. Figure 3.10-4 also depicts some shrinkage in the

insulation in the third and fifth sections of the wall, as well as air

leakage at the top and the bottom of the wall where it intersects the floor

and ceiling.

Around window area

Leakage through wall -floor seams

window seams

Figure 3.9 Sample Defect Observed in the Huron Federal Building

43
Figure 3.10 Thermal Defects Observed in the Huron Building

3.10-1

E wall with NE

entrance off to right

3.10-2

N face with NE

entrance on left

3.10-3

Close-up of middle

section on E wall as shown in 5-2

3.10-4

Fourth floor interior

N wall of the E wing

44
3.2.6 Description of Thermal Defects in the Norfolk Federal Building

The thermal anomalies observed in the federal building in Norfolk, VA

consist of two basic kinds, the leakage at the wall-floor seams and the

leakage at the exterior panel seams (figures 3.11 and 3.12). In figure

3.12-1, there is a great deal of heat loss shown at the panel seams in the

middle of the east wall. The wa 1 1-to-post-to-f loor seams are also sources

of heat loss as illustrated in figures 3.12-2 through 3.12-5. Figure 3.12-

2 shows an interior thermogram of the west wall at the south end. (The

middle window does not have the blind pulled down and is not reflecting.)

Note the vertical, darker area in the center of the picture, which is a beam conducting cold inwards. Figures 3.12-3, 3.12-4, and 3.12-5 show

leakage between the windows and from the panel seams in the solid wall

sections below, which correspond to the horizontal, long, white areas

across the entire length of the building. Other thermal defects observed

include the floors of the third floor and second floor overhangs, as evidenced by the voids in insulation and leakage at the seams identified in

figures 3.12-5 and 3.12-6.

Second floor overhangs

Missing

insulation

Leakage

in seams

Defective areas

Figure 3.11 Sample Defects Observed in the Norfolk Federal Building

45
Figure 3.12 Thermal Defects Observed in the Norfolk Building

3.12-1

Lower wall section

of E wall

3.12-3

W face at the N

end

3.12-5

Third floor overhang

of the N wall at the

W end

3.12-2

W wall at S end of

the third floor

3.12-4

E wall at the

SE corner

3.12-6

NE overhang of second

floor over garage

46
3.2.7 Description of Thermal Defects Observed in the Pittsfield Federal

Building

The thermal integrity of the federal building in Pittsfield, MA can be

characterized by a large number of poorly defined voids in the insulation

(figures 3.13 and 3.14). Many sections have insulation that is distributed

unevenly, and there are areas where a whole section of wall is lacking

insulation as shown in figure 3.14-2, where the top third of the wall next

to the front entrance is distinctly warmer. The large percentage, 18%, of

defective wall observed in the Pittsfield building is due largely to these

large rectangular voids, but there are problems with all types of seams. In figure 3.14-1 for example, note the leakage from the seam below the

second floor windows and the wall-wall seam in the upper right-hand corner. The posts running through the walls also cause heat loss as shown in

figures 3.14-4 and 3.14-6. These two thermograms are characteristic of

those for every wall-post seara in the building. At each corner there is an indentation in which there is leakage as illustrated by the thermograms in

figures 3.14-3 and 3.14-4, where the exterior and the interior of the NW

corner on the first floor are shown. The dark line in figure 3.14-4,

indicating the penetration of cold, corresponds to the bright white regions

in figure 3.14-3 which indicate heat loss to the outside. Other defects

observed in this building include the possibility of a damaged pipe inside

the north wall as shown in figure 3.14-5, where a flaring warm area near

the top is detected.

Leakage through ceiling and corner seams

Figure 3.13 Sample Defects Observed in the Pittsfield Federal Building

47
Figure 3.14 Thermal Defects Observed in the Pittsfield Building

3.14-1

S end of E wall

(exterior)

3.14-2

The front entrance

on E wall (exterior)

3.14-3

NW corner with N

wall section and

indent (exterior)

3.14-5

Center of N wall

(exterior)

3.14-4

NW corner with W

window and

indent (interior)

3.14-6

Wall-post seams on E

wall first floor

( interior)

48
3.2.8 Description of Thermal Defects in the Springfield Federal Building

The Springfield federal building has a relatively low percentage, 7%, of

wall area subject to thermal anomalies (figures 3.15 and 3.16). The main

defects are the post-wall joints as seen in figures 3,16-1 through 3.16-6.

Note the consistent pattern of the defect in figures 3.16-1 and 3.16-3. An

exterior close-up of the post-wall seam is shown in figure 3.16-2 at the SW

corner with an interior view in figure 3.16-4. The dimensions of the

columns are defined in figures 3.16-1 and 3.16-2 by the heat loss that

occurs at the edges as the column rises up the side of the building. The

interior view shows the cold penetrating to the interior at the sides of

the pillar at a single floor. The heat loss from the joints is also

consistently evident at the corners, where there are small insulation voids

above the windows as well, which can be observed in figure 3.16-3 and 3.16-

5. There is also a great deal of heat loss from the glass windows on the

first floor and from the atrium which rises up the center of the east face

of the building, as shown in figures 3.16-5 and 3.16-6.

Wall post at window area

Air penetration at column seams

Exterior

thermogram

Interior

view

Figure 3.15 Sample Defects Observed in the Springfield Federal Building

49
Figure 3.16 Thermal Defects Observed in the Springfield Building

3.16-1

SE corner of

the N wing

3.16-3

SW corner showing seams

at the second and third

floors

glass wall with metal

panel, W end

3.16-2

Close-up of the floor-wall

post seam on the E face of

the N wing

3.16-4

Interior thermogram of

the wall-post seam

center of E face

50
3.3 Conclusions

Though seven of these eight federal office buildings were built to the new

federal energy guidelines, thermographic inspection revealed serious

defects in each building. Thermal defects in the insulation system vere

observed to be in the range of 6 to 18 percent of the wall areas of these

buildings. Leakage around windows and seams were observed in all

buildings. Other thermal anomalies found in these buildings included

missing insulation in the wall, thermal bridges, defective ceiling and

floor insulation, and convection within insulation. Buildings with

overhangs and indentations appeared to have severe problems in those areas.

Thermographic inspections performed on commercial buildings are capable of

determining the thermal integrity of the building envelopes and detecting

defects in the mechanical system. For new buildings, thermography can be

used for quality control during construction. Had such construction-stage

inspections been done on these buildings, most of the observed defects

could have been corrected at no cost to the building owner. After

buildings are occupied, thermographic inspections can still identify

degradation of materials and locations of poor performance of building

envelopes. However, correction of these defects at this stage are costly

and only justified in extreme cases.

51
4. Aerial Infrared Thermographic Inspections

4.1 Introduction

Aerial infrared thermography is an imaging process which produces an apparent radiance temperature map of the inspected terrain. An aerial

thermography survey can be conducted using either infrared imaging

equipment in a helicopter or a line scanner in an aircraft [1]. The

technique is effective in identifying uninsulated roofs, defective roof

insulation or wet insulation regions on built-up roofs. Variations in the

thermal resistance produced by the roof defects cause differences in

apparent radiance temperatures in the roofs displayed in an aerial infrared

image. Flights are most often conducted at altitudes between 1000 and 2000

ft (305 and 610 m). The instantaneous field of view of the infrared

scanner varies with the particular system but will generally range between

1 and 2.5 mil li-radians.

Variations in roof emittance, local wind speed and outdoor temperature

produce differences in radiance temperature which are larger than those

between built-up roofs having 2 and 4 inches of insulation. If all the

built-up roofs displayed in an aerial infrared thermogram are well

insulated, then variations in parameters such as roof emittance, local wind

speed, and local outdoor temperature may cause particular roofs to appear

warmer than other roofs, which may be incorrectly interpreted as the

absence of roof insulation without knowledge of building design. A

potential problem with built-up roofs is that the exterior membrane

ruptures, permitting water to penetrate the roof system and wet the

insulation. Regions having wet insulation will conduct more heat and will

appear warmer than regions having dry insulation. The merit of such a survey technique is that defective regions can be located, permitting

repairs to be carried out instead of replacing the whole roof system.

4.2 Procurement of Aerial Thermographic Services

The aerial infrared thermographic inspections were performed by private

contractors. A two-step process was undertaken which determined the

availability of specialized representative services from competitive

organizations, followed by negotiations based upon submitted proposals.

Contractor costs, equipment, exceptions to requirements, diversity of

geographical locations, and period for performance were sought.

Compilations for contractor services responding organizations with

interest, experience and background specific to building investigations,

and staff capabilities were established from a "sources sought 10 solicitation in the Commerce Business Daily. Competitive proposals for

building inspections were negotiated for contract awards. (See Appendix B

for specification of services.)

The solicitation resulted in 25 responses for the aerial thermography

contractor services. The respondees included companies with building

experience, universities, and others with specialized infrared (IR)

capabilities for military or forest fire surveillance.

52
The responses to proposal bid requests for aerial thermographic surveys are indicated below (bids for more than one

for the three buildings were awarded.

building are included). Contracts

Bids Declined Returned

Federal Building Received bids with no response

Anchorage, AK 2 - -

Springfield, MA 4 1* 2

Columbia, SC 3 1* 1

* Letters indicated that walk-on roof inspection with IR and other

equipment is required.

Comments from potential contractors expressed concern that aerial surveys

may not be useful (particularly for a single building) and walk-on roof

inspections are essential using IR and other equipment (e.g., coresampling). Core-sampling was not allowed by GSA due to concern for long

term durability of the repaired (removed) section.

4.3 Evaluation of Roof Systems by Aerial Thermography

From the responses of the potential contractors and other investigations

[2], it appears that using flyover infrared surveys to identify defects in

building roof systems is not sufficient. Walk-on thermographic inspection

as well as visual investigation must be performed to detect thermal

anomalies accurately. The roof systems of the Anchorage, Columbia and

Springfield office buildings were evaluated by three different contractors.

Summaries of their reports [3, 4, 5] follow.

Figure 4.1 is a thermogram from the aerial thermographic survey performed

on the Springfield building. After the walk-on infrared inspection, no

major thermal anomalies or water damage insulation were found. The

analysis of potential locations of heat loss regions shown in figure 4.1

were explained by equipment under the area (2)* warm air vents and roof

drains (4), metal hatch covers and "corner effects" (7). The extended

bright area at (7), corresponds to vented warm air from wall louvers of the

penthouse (adjacent to the courthouse roof) which may obscure actual roof

surface conditions. One unexplained area (1) in figure 4.1, was the only

potential location which required further study. It should be noted that

the roof of an older building adjacent to the federal building showed

extensive damaged areas ( 9)—( 10).

After the flyover infrared survey was performed on the Columbia building,

the anomalies in the IR images were explained by roof surface conditions

caused by vents, skylights, drains and hatches. Only two locations

required further investigation. One was found to be a build up of gravel

and bitumen, the other produced an IR pattern common to divisions between

wet and dry fiberous insulation board. The areas are shown in figures 4.2

* Numbers in the parenthesis refer to roof areas noted on figure 4.1.

53
(aerial) and 4.3 (walk-on). The source of water intrusion was presumed to

be due to channeling precipitation behind the flashing (from grooves in the

precast exterior wall panels). Since no core samples were taken from the

roof, no further investigation was made to determine the composition of

roof materials, deterioration, and moisture content.

The roof systems for Springfield and Columbia have built-up roofs. The

Anchorage building has an inverted membrane roof with blocks of polystyrene

thermal insulation covered by concrete blocks. An aerial thermographic

inspection and walk-on infrared survey performed on the six modules of the

building did not reveal any areas with thermal deficiencies, except some locations with explainable conditions, such as air vents. However, by

walking the roof, several problems due to "sunken" surfaces could be seen. Removal of the concrete blocks in a few areas showed large gaps between the

insulation boards. These areas were heavily laden with water and

deteriorated, as shown in figure 4.4. Thermography is not a useful

diagnostic tool for the inverted membrane roof since the thermal problems

are masked by the thermally massive concrete blocks. The extent of damage

to the entire roof surface was not determined, since the IR study was the

only contracted service.

4.4 Conclusions

The quality of the aerial thermographic surveys produced by the three

private contractors indicated that aerial thermographic surveys can yield

information from which roof damage can be assessed. For detection of roof

anomalies on single buildings, the economic benefits of aerial thermography

have not been determined. For the multi-building complex or large areas,

aerial surveys have shown that many buildings can be evaluated by flyovers.

Since it is necessary to follow-up with walk-on inspections, the C06t

factors for also conducting the aerial survey may not be justifiable. On

the other hand, the demonstration that all thermal roof problems on a building can be detected without an aerial survey should be undertaken. If

proven, cost savings by elimination of the aerial study may then be

realized.

Roof anomalies revealed through aerial infrared surveys are often not

related to deficiencies resulting from the roofing system. Instead, they are attributable to building system components or equipment. The analysis

of such sources requires building and roof inspections by experienced

and/or trained staff.

Roof-top level inspections with infrared equipment was required to define

potential deficiencies. Other testing, such as core-sampling or water

content measurements in thermal insulation by destructive means, was

recommended by contractors for evaluation of the extent of deterioration.

Thermography did not prove to be a useful tool for inspecting the inverted

membrane roof of the Anchorage federal building. It helped to detect the

beginning of water damage to a section of the roof of the federal building

in Columbia, SC. The repair of this area before extensive damage is done

would prevent the need for replacement of the roof system at a later date.

54
Aerial Photograph

. x

Thermogram

Figure 4.1 Heat loss areas of the Springfield roof system

observed by aerial thermography

55
Figure 4

Figure 4

(a) (b)

2 (a) Aerial photograph and (b) aerial thermogram of the

Columbia building roof system (area of anomaly circled)

i

(a) (b)

3 (a) Photograph and (b) thermogram from walk-on infrared

survey of the Columbia building roof system (lines

enclose area of concern)

56
(a)

(b)

Figure 4.4 (a) Wet polystyrene insulation and (b) deterioration

of the Anchorage building roof system.

57
5.0 Audits Using Spot Radiometers

5.1 Introduction

The spot radiometer is a hand-held device used to radiometrical ly measure

the equivalent blackbody temperature of a relatively small area of a surface [1]. Spot radiometers are calibrated by pointing at a surface of

known temperature and making adjustments such that it determines the

correct temperature of the reference surface (manufacturers frequently

provide reference surfaces). A spot radiometer is used to measure the

inside surface temperature of a building component and the inside air

temperature. Another measuring device is used to measure the coincident

a»ir temperature at the exterior surface. From the three measured

temperatures an estimate of the apparent thermal resistance of the

component can be made. A suitable application is to determine

qualitatively whether a wall is insulated or if insulation voids or other

thermal defects are present.

In performing the measurement, the instrument is pointed at a surface area

of interest and senses the total infrared radiation over a particular

wavelength band emanating from the surface, including both the self-emitted

surface radiation and reflected radiation from surrounding surfaces. The

device is calibrated to read out the apparent radiance temperature on either a digital or meter display. The apparent radiance temperature is

defined as the temperature of a black surface that would radiate the same amount of thermal radiation as a real surface at the same temperature and

having a surface emittance different from unity. Typical specifications

for spot radiometers include a temperature measurement resolution within +_ 0.5 °F (+_ 0.3 °C). Spot radiometers with a resolution of within +_ 0.1°F

(+0.05°C) are also commercially availble. Spot radiometers generally have

their principal spectral response in the range of 10 microns, and a response tiee of less than 2 seconds.

5.2 Thermal Resistance Measurements by Spot Radiometer

The spot radiometer is a non-imaging infrared instrument designed to

measure the net radiative heat-flow from the surface, which includes the

emitted and reflected radiation. At steady state conditions, thermal

resistance of an exterior surface of a building can be established from eq.

5.1.

hi<T i-Tis>

where R is the thermal resistance, hr *f

t

2 *°F/Btu(m2 °K/W)

T£ is the interior air temperature, R(K)

T

q

is the exterior air temperature, R(K)

T- is the inside surface temperature, R(K)

h^ is the inside surface heat transfer coefficient,

Btu/hr *ft 2 *°F (W/m2 *K)

(5.1)

58
The inside surface heat transfer coefficient* hj , can be expressed in eq.

5.2, which includes thermal radiation and convection.

h

£ = a'E*^4 -- T

i8

4 3/(T i”Tig ) + 0sl9 (T i"Tis )0 ‘ 33 (5.2)

where a is the Stefan-Baltzmann constant,

0.1714 x 10“ 8 Btu/hr *ft 2 'R4

(5.67 x 1CT8 W/m2

’K 4

)

E is an emissivity factor which is determined from

1 = 1 + 1 ~ l (5.3)

~~^z

where Ej and E£ are the emissivities of the subject surface and other room

enclosure surfaces, respectively.

Therefore, thermal resistance of an exterior surface can be calculated from

eqs. 5.1, 5.2 and 5.3 with temperature measurements and estimated

emissivities

.

Both the Huron and Ann Arbor buildings were inspected with a general

purpose, dual-range spot radiometer with an indoor scale of 50°F (10°C) to

100°F (38°C) and an outdoor scale of -20°F (-29°C) to 150°F (66°C) [6, 7].

The instrument was equipped with a red filter of 8 to 14 microns to

eliminate the effects of humidity, color, and other emissivity conditions

that would affect the surface temperature readings. Calibration of the

spot radiometer is accomplished by adjusting its zero control to match its

output temperature to the attached surface thermometer of a factorysupplied reference block. The survey at each building was conducted three

hours after sunset and one-half hour after the heating system was turned

off. It was found that the spot radiometer should be left in the "on"

position throughout the inspection to avoid calibration drifts. The

temperatures of the inside and outside air were recorded with a digital

thermometer with a range of -31°F (-14°C) to 122°F (50°C). The accuracy of

both the spot radiometer and the digital thermometer is +. 0.5°F (+ 0.3°C).

Temperature data were collected at certain regions of several surfaces.

The thermal resistance (R-value) of the region was calculated by assuming

0.9 as the surface emissivity. Several spots were inspected on each

surface, their R-values were determined and the average of these R-values

was used to represent the thermal resistance of the surface.

From the architectural design of these two buildings, the R-value of each

building surface component was also calculated following the methodology

specified in the ASHRAE Handbook of Fundamentals [8].

5.3 Results of the Inspection of the Huron and Ann Arbor Federal Building

Tables 5.1 and 5.2 are summaries of measured and design R-values of the

Huron and Ann Arbor buildings, respectively. In general, the measured

thermal resistances of wall areas are lower than the design values and Rvalues of windows and doors are relatively close to the design values in

these two buildings. The discrepancies between the measured and design Rvalues may be due to measurement errors, method of calculation, and

deficiency in construction. Based on the accuracy of the spot radiometer

59
and the digital thermometer (both +. 0.5°F (+_ 0.3°C)), the percentage

variation of measurement versus the temperature difference between inside

air and surface is illustrated in figure 5.1. According to eq. 5.1, the

temperature measurements corresponding to surface components of large R~

values will have a lower temperature difference between inside air and

surface, and thus a higher percentage variation in the measurements as shown in figure 5.1. On the other hand, for surface components with low Rvalues, such as windows and doors, the air to surface temperature

differences are expected to be high and the percentage variation in the

measurements are relatively low. Hence, the measured and design R-values

of these surfaces are much closer to each other (also shown in Table 5.1).

In addition, the equations used to calculate the thermal resistance from

temperature measurements are based on steady state conditions without

considering transient effects of thermal storage in construction materials,

and these effects may cause errors in computing heat transfer across the

building envelope.

Table 5.1 indicates that the measured R-values of office and lobby walls

in the Huron building are much lower than the design values. However,

thermal conductance measurements on the north wall of the south wing using

heat flow meters and calorimeters give much higher R-values of 20.41 and

11.98 hr*f t^*°F/Btu, respectively (see Chapter 8), as compared with 4.54

hr*ft^*°F/Btu from spot radiometer inspections and 15.75 hr'f t^,0F/Btu from

design. The large discrepancy between the measured R-values and the design

values of wall areas are suspected to be due to errors in the spot

radiometer measurement caused by either equipment limitations or the nonsteady state response of the building envelope (see Chapter 8).

The Ann Arbor building was designed such that various wall sections had

different R-values. The measured thermal resistance of surface components

in this building are relatively close to the design values, as given in

Table 5.2. The thermal resistances measured by heat flow meter and

calorimeter of the west wall are 11.53 and 11.05 hr "ft ^*°F /Btu

,

respectively (see Chapter 8), compared with 7.85 hr'f t^”°F/Btu, the design

values. In addition, the Ann Arbor building is not considered to be energy

efficient, with a design R-value of less than 10 hr*ft^°F/Btu for all wall

areas. The measured thermal resistances of surface components by spot

radiometer survey appear to be reasonably accurate.

The utilization of spot radiometers for thermal property measurements has

the advantage of portability, speed, and simple operation. However,

laboratory evaluation of a low-resolution (+_ 0.5°F or +. 0.3°C) spot

radiometers to determine thermal resistance of building walls have shown

that measurements are not accurate [9]. Results from data reduction of

measurements by spot radiometer for both the Huron and Ann Arbor buildings

show discrepancies between the measured R-values and the designed R-values.

Figures 5.2 and 5.3 illustrate the distributions of these R-values as well

as the regression lines based on fits of the entire dataset using least

squares techniques for the Huron and Ann Arbor buildings.

Another field investigation using a high resolution (+_ ,1°F or +_ 0.05°C)

spot radiometer and a radiant flow radiometer (where thermal radiation is

measured without conversion to temperatures) to determine thermal

resistance of test house walls revealed that systematic errors were related

to the heat capacity of wall materials [10].

60
5.4 Procurement of Audits Using Spot Radiometers

The inspection of the small buildings using spot radiometers was procured

by a process similar to that described in Chapter 4 for aerial

thermographic inspection. Appendix C contains the specifications used for

procurement

.

Responses from 12 companies were received to conduct energy audit

inspections with hand held spot radiometers. The summary of responses to

the solicitation to conduct energy audits with a spot radiometer is shown

below (with bids for more than one building). Contracts for three

buildings were awarded. Due to the lack of cold weather conditions the

Pittsfield study was not performed.

Federal Building

Bids

Received

Declined

Bids

Returned with No

Response

Pittsfield, MA 3 1 * 2

Ann Arbor, MI 3 1 * 2

Huron , SD 3 1 * 2

* Letter indicated spot radiometers not useful for the intended purpose.

5.5 Conclusions

Results from spot radiometer inspections performed on two office buildings

indicated there were larger discrepancies in the results for surface

components of high R-values than those of low R-values. This may be due to

the sensitivity of the instrument as well as inappropriateness of the

steady state assumption used to derive the equations used for calculations.

However, the thermal resistance values of building exterior surfaces

provided qualitative indications of the surface's thermal performance,

though the absolute measurements lacked accuracy. Due to the simplicity

and portability of the spot radiometer, it can be used to qualitatively

evaluate regions of building envelope components.

61
Table 5.1

Comparison of Thermal Resistance Measured by Spot Radiometer

with Design Values in the Huron Building

Averag;e Measured R-Values Design

hr’ft. °F/Btu (m2-°C/W) R-values

North Wing South Wing hr’ft 2 *°F/Btu

West South North East North East Lobby (m^G/W)

Office wall 6.18 6.35 5.44 5.86 4.54 6.10 _ 15.75

(1.09) (1.12) (0.96) (1.03) (0.80) (1.07) - (2.77)

Walls under 3.28 3.46 2.69 4.03 — 4.07 3.12 12.15

windows (0.58) (0.61) (0.47) (0.71) - (0.72) (0.55) (2.14)

Stairway — - - 4.03 4.72 - - 7.47

walls — “* — (0.71) (0.88) — (1.32)

Garage wall - 1.73 - - - — - 2.35

— (0.30) — — — — — (0.41)

Garage roof — 1.65 — — - — - 5.47

- (0.29) - — - - - (0.96)

Column walls _ — 3.54 — — - 5.10 -

- - (0.62) - - - (0.90) -

Doors 1.50 — — — — — - 1.69

(0.26) - - - - - - (0.30)

— _ - - - - 1.26 0.90

- - - - - - (0.22) (0.16)

Windows with 3.40 3.19 3,18 — — 3.65 2.14 - curtains (0.60) (0.56) (0.56) — — (0.64) (0.38)

windows without — — — — 1.79 - 2.04

curtains — — — - - (0.32) - (0.36)

Lobby wall — — — — _ 4.06 14.50

- - - - - _ (0.71) (2.55)

62
Table 5.2

Comparison of Thermal Resistance Measured by

Spot Radiometer with Design Values in the Ann Arbor Building

Average Measured R-Values

hr*f t 2,0F/Btu

(m2-°C/W)

Design

R-va lues

hr*ft 2, °F/Btu

West South East North Lobby (m^C/W)

Office Walls

Type 1 7.85 - — 9.19 8.53 8.40

(1.38) - - (1.62) (1.50) (1.48)

Type 2 5.71 6.71 - - - 8.77

(1.01) (1.18) - - - (1.54)

Type 3 - 4.42 5.71 - — 9.04

- (0.78) (1.01) - — (1.59)

Type 4

- 4.42 3.15 6.08 5.65 4.54

- (0.78) (0.55) (1.07) (0.99) (0.80)

Lobby Walls

Type 1 - - - - 3.40 4.62

— — — - (0.60) (0.81)

Type 2 - - - - 2.67 2.12

— - - - (0.47) (0.37)

Windows

Vertical - — 1.22 1.53 2.04

- - (0.21) (0.27) - (0.36)

Horizontal - — 1.27 1.38 _ 1.69

- - (0.22) (0.24) - (0.30)

Bay - 1.09 — 0.94 — 0.90

— (0.19) - (0.17) - (0.16)

Doors - - — 1.52 _ 1.69

- - - (0.26) - (0.30)

63
-VALUE

FROM

MEASUREMENT

(m 2

°C/W)

TEMPERATURE DIFFERENCE (° F) 0 5 10 15 20 25 30 35 40

Figure 5.1 Percentage variation of measured R-values from spot

radiometer versus temperature difference of inside

air and surface

Figure 5.2 Thermal resistance (R-value) of spot radiometer

measurement versus design for the Huron building
-VALUE

FROM

MEASUREMENT

<m 2

.°C/W)

CC

Figure 5.

R-VALUE FROM DESIGN (hr ft 2 - °F/Btu) 0 2 4 6 8 10 12 14 16 18

3 Thermal resistance (R-value) of spot radiometer

measurement versus design of the Ann Arbor building.

65
6. Air Infiltration and Ventilation Rate Measurements

6.1 Introduction

The air infiltration and ventilation rates of the eight federal office

buildings were tested using tracer gas techniques [1]. The measurement

employed the tracer gas decay method using sulfur hexafluoride (SFg) as the

tracer. This test was designed for each building to produce a measure of

the total air infiltration rate of the building and the rates of the major

zones of the building. Sample and injection tubing was installed in each

zone along with wiring for measuring interior temperatures, the status of

the building's HVAC fans and exterior weather conditions (wind speed, wind

direction and exterior temperature). The automatic air infiltration system

previously designed by NBS for large buildings was installed in each

building for a period of about a week during the fall, winter and spring

(three automated air infiltration systems were used on this project).

Tests were performed both during periods of occupancy and non-occupancy,

with the outside air intake dampers operated normally and closed,

respectively. Tracer gas measurements were made for a total of about 200

hours in each building. The air sample locations for these tests are given

in Table 6.1, and shown in the building schematics in figures 2.2 through

2 . 8 .

6.2 Results of the Air Infiltration Tests

The summary of the infiltration measurement results in Table 6.2 show

average infiltration rates under winter conditions, neglecting extremely

high wind speeds. These measurements are made with all outside air intake

and exhaust dampers closed. These results indicate that the buildings in

Huron and Anchorage are experiencing relatively low natural leakage rates.

The buildings with the highest natural rates are Ann Arbor, Norfolk and

Springfield. By using the results of these tests it is possible to

estimate the contribution of air infiltration to the design load of the

buildings. These estimates are also included in Table 6.2. As can be

seen, the air infiltration contributed from 23% to 61% of the building

heating load. Tables 6.3 through 6.7 show examples of typical one-hour

decay tests for the buildings in Anchorage, Springfield, Norfolk, Huron and

Columbia. These tables indicate the extent of tracer gas mixing obtained

in these tests, with good mixing being a requirement for accurate results.

They also show zones of the building which exhibit high air exchange rates

compared to the rest of the building - the lobby in Springfield, the 1st

floor in Norfolk, and the lobby in Columbia. Similarly high rates can also

be shown for the 1st floor in Fayetteville and the lobby and post office in

Ann Arbor. The lobbies generally exhibit larger exchange rates due to the

exterior doors in these zones and the people moving in and out of the

building. The post office in Ann Arbor has a large amount of such

pedestrian traffic, and large, leaky doors for loading and unloading mail.

The data of the form shown in Tables 6.3 to 6.7 were checked for accuracy

and then stored in separate files according to the condition of the vents

and occupancy of the building. Tables 6.8 and 6.9 show data from these

files for the Ann Arbor building. Note the large ventilation rates in

Table 6.9. These rates were measured during the spring season when the

outdoor air is cool enough to condition the building without running the

chillers

.

66
Table 6.1 Tracer Gas Sampling Locations

Anchorage

1 . Module A

2. Module B

3. Module C

4. Module D

5. Module E

6. Module F

7. 5th Floor Module C

8. 3rd Floor Module C

9. 1st Floor Module C

Springfield

1. North Return

2. South Return

3. Atrium/Lobby

4. 5th Floor - North

5. 4th Floor - North

6. 3rd Floor - North

7 . 2nd Floor - North

8. 1st Floor - North

9. 4th Floor - South

10.2nd Floor - South

Ann Arbor

1 . HVAC Return

2. 4th Floor Return

3. 3rd Floor Return

4. 1st & 2nd Floor Return

5. Lobby

6. Post office

Huron

1. North Return

2. East Return

3. 4th Floor ~ North

4. 3rd Floor - North

5. 2nd Floor - North

6. 1st Floor - North

7. 4th Floor - East

8. 3rd Floor - East

9. 2nd Floor - East

10 . 1st Floor - East

Co lumb ia

1. HVAC Return

2. 13th Floor

3. 11th Floor

4. 9th Floor

5. 7th Floor

6. 5th Floor

7. 3rd Floor

8. 1st Floor & Basement

9. Lobby

10.

Courthouse

Norfolk

1. HVAC Return

2. 8th Floor

3. 7th Floor

4. 6th Floor

5. 5th Floor

6. 4th Floor

7. 3rd Floor

8. 2nd Floor

9. 1st Floor

Fayetteville

1. 1st Floor

2. 2nd Floor

3. 3rd Floor

4. 4th Floor

5. 5th Floor

6. Courtroom - 5th Floor

Pittsfield

1. 1st Floor Return

2. 2nd Floor Return

67
Table 6.2

Anchorage

Ann Arbor

Columbia

Fayetteville

Huron

Norfolk

Pittsfield

Springfield

Average Air Infiltration Rates of Each

Federal Building

Changes per Hour

0.28

0.70

0.40

0.33

0.20

0.52

0.32

0.52

Percent of Design Heat Load

55%

48%

52%

23%

30%

52%

30%

61%

68
Table 6.3

Typical One-Hour Decay Test for Anchorage

FEDERAL BLDG. - ANCHORAGE 1/ 7/83 12

MAX CURRENT = 1750 MIN CURRENT = 1708

EXTERIOR TEMP. = -18.2 C WIND SPEED = 3.9 M/S WIND DIR. = 135.

+/- .1C +/- .8 M/S

INTERIOR TEMPERATURES

MOD A MOD B MOD C MOD D MOD E MOD F 1ST C 3RD C 5TH C

22.5 22.3 0.0 0.0 23.3 23.5 22.6 22.7 22.7 C

+/- .7 . 1 0.0 0.0 0. 0 0.0 .4 0.0 0.0 C

HV AC FAN OPERATION

MOD A MOD B MOD C MOD D MOD E MOD F

3599 3599 3599 3599 3599 3599 SEC

TRACER CONCENTRATIONS

MOD A MOD B MOD C MOD D MOD E MOD F 1ST C 3RD C 5TH C

12:00 114.6 108.9 101.1 91.8 78.2 81.4 68.2 86.5 103.3 PPb

12:10 105.0 98.2 99.9 88.2 76.1 77.7 62.3 78.6 97.4 PPb

12:20 102.6 96.6 92.4 83.2 73.7 74.6 49.9 76.6 97.6 PPb

12:30 93.9 90. 1 89.3 82.2 69.2 69.2 46.3 72. 8 130.3 PPb

12:40 91.2 84.3 79.0 76.8 65.64.1 48.9 66.1 80.9 PPb

INFIL .31 .32 .44 .26 .32 .39 .48 .34 . 1

6

/HR

Table 6.4

Typical One-Hour Decay Test for Springfield

FEDERAL BLDG. - SPRINGFIELD, M 12/ 2/82 0

MAX CURRENT = 1862 MIN CURRENT = 1810

EXTERIOR TEMP. = 12.1 C WIND SPEED = 1 . 3 M/S WIND DIR. = 247.

+/- .1C +/- .6 M/S

INTERIOR TEMPERATURES

NORTH SOUTH LOBBY N 5TH N 4TH N 3RD N 2ND N 1ST S 4TH S 2ND

23.4 24.3 27.8 24.7 23.7 23.4 23.0 24.3 24.5 24.3 C

+/- .2 . 1 0 . 0 . 1 . 1 . 1 . 1 . 1 . 1 0 . 0 C

HV AC FAN OPERATION

NORTH SOUTH ATRIUM

0 0 0 0 SEC

TRACER CONCENTRATIONS

NORTH SOUTH LOBBY N 5TH N 4TH N 3RD N 2ND N 1ST S 4TH S 2ND

0:00 176.3 220.0 177.0 161.2 156.7 155.9 159.9 135.4 215.6 203. 1 PPb

0:10 144.5 195.5 149.9 148.0 149.8 148. 0 146.1 128.6 206.1 192. 8 ppb

0:20 138.4 179.2 140. 8 142.3 138.7 141.5 133.1 121.4 196.1 177.0 Ppb

0:30 130.2 175.0 126.0 136.2 132.

134.1 131.3 109.9 185.4 176.3 PPb

0:40 127.6 164.6 119.9 123.9 121.9 129.6 126.1 109.4 173.8 166.9 PPb

INFIL .26 .32 .47 .35 .40 .27 .27 .35 .34 .26 /HR

DEG

DEG

69
Table 6.5

Typical One-Hour Decay Test for Norfolk

FEDERAL BUILDING - NORFOLK, VA 10/21/82

MAX iCURRENT = 1665 MIN CURRENT 1621

EXTERIOR TEMP . = 17.5 C WIND SPEED = 2.0 M/S WIND DIR.

+/- 0.0 c +/- . 6 M/S

INTERIOR TEMPERATURES

RET 8TH F 7TH F 6TH F 5TH F 4TH F 3RD F 2ND F 1ST F

25.7 25.7 25.4 24.6 24.7 24.7 24.8 24.4 23.5 C

+/- . 1 0. 0 .2 0.0 0 . 0 0.0 0 . 0 0 . 0 0 . 0 r

HV AC FAN OPERATION

M HV AC 1ST FL

0 0 SEC

TRACER CONCENTRATIONS

RET 8TH F 7TH F 6TH F 5TH F 4TH F 3RD F 2ND F 1ST F

0:00 137.9 107.2 128.5 126.4 119.0 120.9 127.4 114.9 68.0 ppb

0:10 126.9 95.6 116.0 118. 1 111.1 113.7 118.7 106.6 51.9 ppb

0:20 117.1 90.1 111.7 112.1 106.5 106.6 112.7 93.8 49.3 ppb

0:30 111.1 84.1 101.7 106.9 96.9 97.1 105.7 86.4 36.5 ppb

0:40 101.7 77.3 97.9 98.0 92.7 88.2 98.4 79.7 30.0 ppb

INFIL .43 .42 .36 .36 .38 .51 on oo

. .57 1.17 /HR

Table 6.6

Typical One-Hour Decay Test for Huron

FEDERAL BUILDING - HURON, S.D.

MAX CURRENT = 659 MIN CURRENT = EXTERIOR TEMP. = 10.2 C WIND SPEED = 1.5 M/S

+/- .6 C +/- .9 M/S

10/ 8/82 11

611

WIND DIR. = 135. DEG.

INTERIOR TEMPERATURES

N RET E RET N 4TH N 3RD N 2ND N 1ST

26.0 24.4 25.9 27.0 26.0 24.6 C

+/- .6 0 . 0 . 1 .3 . 1 0 . 0 C

HV AC FAN OPERATION

ZONE 1 ZONE 2

594 595 SEC

TRACER CONCENTRATIONS

N RET E RET N 4TH N 3RD N 2ND N 1ST

11:00 99.8 121.4 99.5 95.2 96.9 93.1 ppb

11:10 89.8 88.8 89.9 87.9 86.0 86.9 ppb

11:20 82.7 77.6 83.5 84.8 82.9 84.4 ppb

11:30 82. 1 76.1 82.

81.3 82.4 81.6 ppb

11:40 78.6 75.

81.4 80.9 80. 8 78.3 ppb

INFIL . 24 .31 .19 .17 .12 .21 /HR

70
Table 6.7

Typical One-Hour Decay Test for Columbia

0

157. DEG.

INTERIOR TEMPERATURES

M RET 13 FL 11 FL 9 FL 7 FL 5 FL 3 FL 1ST-B LOBBY COURT

27.6 27.7 27.2 27.5 27.2 26.6 26.3 22.2 21.7 24.3 C

+/- .4 0.0 0.0 0.0 0.0 .1 0.0 0.0 .1 0.0 C

HV AC FAN OPERATION

TOWER000 1 ST -BAS COURT

SEC

EXTERIOR

FEDERAL BUILDING - COLUMBIA

MAX CURRENT = 1708 MIN CURRENT = TEMP. = 14.6 C WIND SPEED = 1.0 M/S

+/- .1C +/- .6 M/S

11 / 19/82

1660

WIND DIR. =

TRACER CONCENTRATIONS

M RET 13 FL 11 FL 9 FL 7 FL 5 FL 3 FL 1ST-B LOBBY COURT

0:00 96.1 94.4 85.6 91.3 85.0 84.9 92.2 32.9 33.3 44.9 ppb

0:10 86.3 89.8 80. 5 88. 0 84.6 80,5 91.0 28. 1 29.0 42.3 PPb

0:20 82. 0 86.

5

78.2 85.5 79.4 78.3 89.2 27.8 26.4 39.8 ppb

0:30 78.4 83.6 74.0 80. 8 78.6 75.7 84.2 24.5 25.0 37.6 ppb

0:40 75.5 80.5 70.6 77.2 72. 0 69.8 79.7 23.8 22.4 35.8 ppb

INFIL .27 .22 .27 .27 .30 .28 .27 .37 .50 .34 /HR

71
Table 6.8

Data Files for Ann Arbor Building with No Outside Air Intake

CITY AND BUILDING : FEDERAL BUILDING - ANNARBOR

CONDITION : 0% OUTSIDE AIR

CONDITION : VENTS UNSEALED

CONDITION : WIND DATA

DATE

2/ 4/83

HOUR

18

W. SPEED

1.4

W. DIR

270. 0

T . OUT

1.4

T. IN

22.9

T.DIFF

21.5

AI. AVE

.86

HV AC

4TH F

3RD F

1&2 F

LOB . P. 0.

= .47

= .71

= .39

= .57

= .76

= 2.28

DATE

2/ 4/83

HOUR

19

W. SPEED

1 . 1 W. DIR

270. 0

T. OUT

1 .8

T. IN

22.7

T.DIFF

20.9

AI. AVE

.95

HV AC

4TH F

3RD F

1 &2 F

LOB . P. 0.

= 1 .24

= 1 . 01

= . 54

= .52

= .97

= 1.43

DATE

2/ 4/83

HOUR

20

W. SPEED

1.0

W.DIR

270. 0

T . OUT

1.5

T. IN

22.5

T.DIFF

21.0

AI. AVE

.81

HV AC

4TH F

3RD F

1&2 F

LOB . P.O.

= .62

= .42

= .62

= .58

= 1.22

= 1.37

DATE

2/ 4/83

HOUR

21

W. SPEED

1.0

W.DIR

270. 0

T . OUT

.8

T . IN

22.3

T.DIFF

20.8

AI. AVE

.93

HV AC

3RD F

1&2 F

LOB . P.O.

= .54

= .64

= . 66

= 1.53

= 1.26

DATE

2/ 4/83

HOUR

22

W. SPEED

.8

W.DIR

270. 0

T. OUT

1.4

T. IN

22. 1 T.DIFF

20.7

AI. AVE

.82

HV AC

4TH F

3RD F

1 &2 F

LOB . P.O.

= .61

= .57

= .64

= .62

= 1.27

= 1.23

72
Table 6.9

Data Files for Ann Arbor Building with Outside Air Intake

CITY AND BUILDING : FEDERAL BUILDING - ANN ARBOR

CONDITION : AIR INTAKE

CONDITION : VENTS UNSEALED

CONDITION : WIND DATA

DATE

5/25/83

HOUR

8

W. SPEED

1.8

W.DIR

157.5

T . OUT

15.0

T . IN

24.0

T.DIFF

9.0

AI. AVE

3.22

HV AC

4TH F

3RD F

2ND F

1ST F

LOB .

= 3.19

= 3.90

= 3.38

= 3.98

= 2.94

= 1.90

DATE

5/25/83

HOUR

9

W. SPEED

1.5

W.DIR

247.5

T . OUT

14.3

T. IN

23.8

T.DIFF

9.5

AI. AVE

2.11

HV AC

4TH F

3RD F

2ND F

1ST F

LOB .

= 2.51

= 1.82

= 2.58

= 2.51

= 1.25

= 1.97

DATE

5/25/83

HOUR

10

W. SPEED

2.0

W.DIR

270. 0

T . OUT

13.8

T. IN

23.6

T.DIFF

9.8

AI. AVE

2.32

HV AC

4TH F

3RD F

2ND F

1ST F

LOB .

= 3.00

= 2.96

= 2.78

= 2.85

= .51

- 1.83

DATE

5/25/83

HOUR

11

W. SPEED

1.9

W.DIR

270. 0

T . OUT

13.8

T . IN

23.6

T.DIFF

9.8

AI. AVE

2.58

HV AC

4TH F

3RD F

2ND F

1ST F

LOB .

= 3.24

= 2.52

= 3.00

= 2.71

= 1 . 86

= 2. 17

DATE

5/25/83

HOUR

12

W. SPEED

1.9

W.DIR

270. 0

T . OUT

14.2

T. IN

23.5

T.DIFF

9.3

AI. AVE

2.73

HV AC = 2.78

4TH F = 3.34

3RD F = 3.10

2ND F = 3.71

1ST F = 1.65

LOB . = 1.79

73
The air infiltration rates for each building are plotted against insideoutside temperature difference AT in figure 6.1. Among the eight buildings

there are varying degrees of dependence of infiltration on temperature

difference. The most noticeable dependence occurs in the cases of Ann

Arbor, Huron, Norfolk and Springfield. These buildings, with the exception

of Huron, are also the leakiest. The lines shown in figure 6.1 are based

on linear regressions of infiltration against temperature difference for

positive values of AT. The equations of these lines for the eight cities

are given by:

Anchorage:

Ann Arbor:

Columbia:

I =

I =

0.164

0.444

I = 0.333

Fayetteville: I = 0.243

+ 0.0019 AT (°F ) ; r

2

(0.0034 AT (°C))

+ 0.0062 AT (°F ) ; r

2

(0.0111 AT (°C))

+ 0.0026 AT (°F); r

2

(0.0047 AT (°C))

+ 0.0023 AT (°F); r

2 (0.0042 AT (°C))

Huron

Norfolk:

I = 0.107 + 0.0026 AT (°F); r

2

(0.0046 AT (°C))

I = 0.464 + 0.0035 AT (°F); r

2

(0.0064 AT (°C))

Pittsfield: I = 0.351

Springfield: I = 0.167

- 0.0016 AT (°F); r

2

(0.0029 AT (°C))

+ 0.0094 AT (°F ) ; r

2

(0.0169 AT (°C))

.180; s = .071

.352; s = .112

.052; s = .117

.151; s = .062

.255; s = .055

.287; s = .082

.021; s = .113

.275; s = .121

s is the standard error of the estimate. Some of the buildings'

1 infiltration rates also exhibited a dependence on wind speed u. Figure 6.2

shows several plots of infiltration versus u, with regression lines drawn

in. The equations of these lines are given by the following:

Ann Arbor: AT from 68 to 77°F (20 to 25°C):

I = 0.399 + 0.051u (mph) (0.113u (m/s)); r

2 = .414; s - .145

Fayetteville: AT from 32 to 41°F (0 to 5°C)

I = -0.174 + 0.102u (mph) (0.228u (m/s)); r

2 = .672; s = .206

Huron: AT from 68 to 77°F (20 to 25°C):

I = 0.225 + 0 . QQ46u (mph) (0.0102u (m/s)); r

2 = .221; s = .024

Huron: AT from 77 to 86°F (25 to 30°C):

I = 0.205 + 0.0081u (mph) (0.0181u (m/s)); r

2 = .131; s = .054

Tables 6.10 through 6.17 give mean measured infiltration rates for each

building within various ranges of temperature difference. Means are given

for wind speeds less than 4.5 mph (2.0 m/s) and greater than 4.5 mph (2.0

m/s )

.
Temperature

Difference

Bin Wind < 4. 5 mph ( 2

.

0 m/s) Wind > 4.5 mnh (2.0 m/s

)

°F (°c) (X/HR) (X/HR)

0, 18 (0, 10) 0.19 -

18, 36 (10, 20) 0.20 0.23

36, 54 (20, 30) 0.38 0.24

54, 72 (30, 40) 0.25 0.31

Table 6.10 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied Periods with

Dampers Closed - Anchorage, AK

Temperature

Difference

Bin Wind < 4. 5 mnh ( 2

.

0 m/s) Wind > 4.5 mph (2.0 m/s)

°F (°c) (X/HR) (X/HR)

-18, 0 (-10, 0) 0.40 0.40

0, 18 (0, 10) 0.37 0.33

18,36 (10, 20) 0.41 0.38

36, 54 (20, 30) 0.34 0.51

Table 6.11 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Columbia, SC

75
Temperature

Difference

Bin Wind < 4.5 mph (2.0 m/ s

)

Wind >4.5 mph

°F (°c) (X/HR) (X/HR)

-36, -18 (-20, -10) 0.56 -

H

00 o o O

t—

1

1 0.56 0.55

0, 18 (0, 10) 0.50 0.50

18, 36 (10, 20) 0.49 0.54

Table 6.12 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Norfolk, VA

Temperature

Difference

Bin Wind < 4.5 mph (2.0 m/s) Wind > 4.5 mph (2.0 i

°F (°c) (X/HR) (X/HR)

-18, 0 (-10, 0) 0.38 0.35

0, 18 (0, 10) 0.44 -

18, 36 (10, 20) 0.43 0.56

36, 54 (20, 30) 0.55 0.53

Table 6.13 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Springfield, MA

76
Temperature

Difference

Bin Wind < 4.5 mnh (2.0 m/s) Wind > 4.5 mph (2.0

°F (°c) (X/HR) (X/HR)

-18, 0 (-10, 0) 0.25 -

0, 18 (,0 10) 0.29 0.37

18, 36 (10, 20) 0.36 0.31

36, 54 (20, 30) 0.26 -

Table 6.14 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Pittsfield, MA

Temperature

Difference

Bin Wind < 4.5 mph (2.0 m/s) Wind > 4.5 mph (2.0 m/s)

°F (°c) (X/HR) (X/HR)

0, 18 (0, 10) 0.13 0.14

18, 36 (10, 20) 0.10 0.11

36, 54 (20, 30) 0.23 0.26

54, 72 (30, 40) 0.26 0.26

72, 90 (40, 50) 0.26 -

Table 6.15 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Huron, SD

77
Temperature

Difference

Bin Wind < 4.5 moh (2.0 m/s) Wind > 4.5 mph (2.0 m/s)

°F (°C) (X/HR) (X/HR)

-18, 0 (-10, 0) .370

0, 18 (0, 10) 0.28 0.50

18, 36 (10, 20) 0.29 0.35

36, 54 (20, 30) 0.39 0.35

Table 6.16 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Fayettevile, AR

Temperature

Difference

Bin Wind < 4.5 mph (2.0 m/s

)

Wind > 4.5 mph (2.0 m/s)

Op (°C) (X/HR) (X/HR)

0 , 18 (0, 10) 0.53 0.52

18,36 (10, 20) 0.59 0.64

36 , 54 (20, 30) 0.61 0.73

Table 6.17 Average Air Exchange Rates in Various Temperature

Difference Bins During Unoccupied periods with

Dampers Closed - Ann Arbor, MI

78
INFILTRATION

RATE

(HR'

1)

ANCHORAGE: UNOCCUPIED INFILTRATION RATE VS. TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) 0 20 40 60 60

ANN ARBOR: UNOCCUPIED INFILTRATION RATE VS. TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) 0 10 20 30 40 50

FAYETTEVILLE: UNOCCUPIED INFILTRATION RATE VS

TEMPERATURE DIFFERENCE

COLUMBIA: UNOCCUPIED INFILTRATION RATE VS. TEMPERATURE DIFFERENCE

(Wind speed < 4.5 mph)

TEMPERATURE DIFFERENCE (°F) 10 20 30 40 50

Figure 6.1 Infiltration Rate Versus Temperature Difference

79
INFILTRATION

RATE

(HR’

1)

Figure 6.1 (continued) Infiltration Rates Versus Temperature Difference

80
INFILTRATION

RATE

(HR

-1)

ANN ARBOR: UNOCCUPIED INFILTRATION RATE VS. WIND SPEED

[AT: 11.1 to 13.9°F (20 to 25°C)]

WIND SPEED (mph) 0 2 4 6 8 10 FAYETTEVILLE: UNOCCUPIED INFILTRATION RATE VS. WIND SPEED [AT: 0 to 2.8°F (0 to 5°C)]

WIND SPEED (mph) 0 2 4 6 8 10 12 14

Figure 6.2 Infiltration Rates Versus Wind Speed

81
6.3 Measured Ventilation Rates

In most of the buildings the measured ventilation rates exhibit a seasonal

dependence such that the lowest ventilation rates occur during maximum

heating and cooling loads. This can be seen in the ventilation rate versus

inside-outside temperature difference plots for each federal building

shown in figure 6.3. Table 6.18 shows mean ventilation rates, along with

the standard deviations of these means, for 9°F (5°C) intervals of

temperature difference for all eight buildings. The mean ventilation rates

can be somewhat misleading for mild temperature conditions. Buildings with

enthalpy control are operated at low or high ventilation rates at the same outside temperature because of differences in outside humidity. This

variation in ventilation rate at the same outside temperature also occurs

in buildings with other types of control systems. Also, as discussed

below, the ventilation rate at a given temperature can be affected by

weather conditions in buildings for which weather induced infiltration is a significant portion of the total ventilation rate.

Figure 6.3 shows the ventilation rate in the Anchorage federal building as

a function of temperature difference. There are low ventilation rates,

about 0.25 to 0.50 exchanges per hour, during cold outside conditions and

higher ventilation rates for temperature differences below 36°F (20°C).

None of the measurements in Anchorage were made under conditions which were warm enough for the building's air conditioning system to be used for

cooling and for the ventilation rate to again be minimized.

Figure 6.3 also shows the ventilation rate of the Ann Arbor federal

building plotted against temperature difference. These data exhibit a large amount of scatter due in part to some very high ventilation rates

induced by high wind speeds. This implies that the infiltration rate of

the Ann Arbor building was strongly dependent on wind speed and that

infiltration became a significant portion of the net ventilation rate under

windy conditions. Figure 6.4 includes a plot of these ventilation rates versus wind speed for a limited range of temperature difference, and indeed

a strong dependence is evident. A similar dependence of infiltration on wind speed was noted earlier in figure 6.2. These large, wind induced

rates were not considered in calculating the Ann Arbor mean ventilation

rates in table 6.18. Under cold outside conditions, AT > 36°F (20°C), this

building was operated at about 0.5 exchanges per hour. For milder

temperatures, outside air was used to cool the building with ventilation

rates as large as 3.0 exchanges per hour. When the temperature difference

was close to zero, the ventilation rates did return to 0.5 exchanges per

hour. Thus, in the Ann Arbor building, the summer and winter ventilation

rates were similar.

The Columbia building's ventilation rates cover a wide range of warm

temperature conditions (AT from -18 to 9°F (-10 to 5°C)), but there is no

clear dependence of ventilation rate on temperature difference for the

summer. If the weather dependent natural ventilation, or infiltration, is

a large fraction of the net ventilation rate which was measured, then the

data may show a dependence on temperature difference. Such a dependence

would tend to imply that infiltration is similar in magnitude to the

>tentional ventilation.

82
When the Fayetteville building is being heated or cooled, the ventilation

rate is about 0.35 exchanges per hour. Under mild temperature conditions,

T from 0 to 9°F (0 to 5°C), the ventilation rate varies between 0.35 and

1.5 exchanges per hour. The ten high ventilation rates between 1.0 and 1.5

exchanges per hour were measured under very windy conditions and probably

were due to a dominance of natural ventilation or infiltration, as in the

Ann Arbor building. Attempts to pressure test this building using its own supply fans, while successful in the other seven federal buildings, were

unsuccessful in Fayetteville because the ventilation system could not bring

in enough outside air to raise the internal pressure significantly. Thus,

the ventilation rates of 1.0 exchanges per hour and higher are probably not

due to mechanical ventilation alone and contain a large component of

natural ventilation induced by the high wind speeds during these

measurements. The wind speed dependence of infiltration for this building

is evident in figure 6.4.

The Huron building has the lowest ventilation rates of all the buildings

examined. Under hot and cold outside temperature conditions, ventilation

rates of 0.2 exchanges per hour and less were measured. The cold weather

ventilation measurements exhibit a dependence on both wind speed and

temperature difference. This is the only building which showed a significant dependence of measured ventilation rate on temperature

difference.

Figure 6.1 shows the dependence of infiltration on AT for this building,

which also appears in the ventilation data. The Huron ventilation rates in

figure 6.3 exhibit additional scatter due to wind effects. Figure 6.4

contains two plots of ventilation versus wind speed in the Huron building

for two different ranges of temperature difference. Plots of infiltration

versus wind speed, shown in figure 6.2, for the same building also show

some dependence, though not as strong as for ventilation. It is possible

that the wind effects are enhanced when the outside air intake dampers are open.

In the Norfolk building the winter and summer ventilation rates are

comparable, both around 0.6 to 0.7 exchanges per hour. In the Pittsfield

building, the minimum ventilation rates during cold weather are lower than

the warm weather ventilation rates.

The Springfield building ventilation rates exhibit an unusual pattern. The

ventilation rates under warm conditions, AT < 18°F (10°C) are relatively

constant at about 0.6 exchanges per hour. For temperature differences

greater than about 27°F (15°C), the ventilation rate varies from a minimum

of 0.6 to a maximum of about 1.25 exchanges per hour. It is not clear if

the high ventilation rates are due to intentional outside air intake, or to a strong dependence of infiltration on temperature difference. The outside

air intake is controlled to maintain the supply air temperature at about

55°F (13°C). This is indeed the temperature difference at which the

ventilation rate is seen to increase. Measurements of infiltration made

with the outside air dampers closed show a similar, but less extreme,

dependence on temperature difference (see figure 6.1). Thus the dependence

of the net measured ventilation on AT appears to be a combination of the

outside air intake control strategy and a significant portion of

temperature dependent infiltration.

83
6.4 Minimum Ventilation Requirements

The measurements of actual ventilation rates in occupied office buildings

are compared to ventilation standards and design specifications of minimum

fresh air intake. A certain minimum ventilation rate must be maintained to

remove pollutants generated inside a building. These minimum ventilation

rates are determined by the building occupancy level (number of people per

1,000 ft^ (100 m^) of floor area) and the extent and nature of the

activities within the building (smoking, painting and other pollutant

generating activities). In some of the buildings, the mechanical equipment

specifications give a minimum outside air intake level in units of

volumetric air flow. Another commonly accepted minimum ventilation rate is

equal to 10% of the HVAC system's total airflow rate. The American Society

of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has

established minimum recommended building ventilation rates which are a function of occupancy levels, building type (e.g., office, store, hotel)

and room type (e.g. kitchen, office, conference room) [12],

Table 6.19 lists the minimum ventilation rates, in units of exchanges per

hour, based on 10% of total air for all the buildings. The minimum

ventilation rates based on ASHRAE standard 62-81 [12] are also included for

the cases of both smoking and non-smoking occupants in office buildings.

In order to determine the recommended ventilation rate from the ASHRAE

standard one needs to know the floor areas of each type of room in the

building and the occupancy levels in each room. Since the occupancy levels

in the buildings are not known, seven persons per 1,000 ft^ (100 m^) of

floor area was used, which ASHRAE recommends when design or actual

occupancy is not known. All the floor area was assumed to be office space,

neglecting the fact that there are kitchens, bathrooms, conference rooms and waiting areas. At the estimated occupancy level for office space,

ASHRAE recommends 20 cfm per person (10 L/s’person) when the occupants

smoke and 5 cfm (2.5 L/s) when they do not smoke. When smoking is

permitted, ASHRAE recommends using the ventilation rate for smoking

conditions. Finally, the table lists a representative value for the

minimum measured ventilation rate in each building.

In all the buildings, except Fayetteville, the 10% total air rate is less

than the ASHRAE recommendation for smoking conditions. In Anchorage and

Norfolk, the smoking rate is twice the 10% ventilation rate. The ASHRAE

non-smoking value is less than all the 10% rates. Since smoking is

permitted in all the buildings, the non-smoking recommendation is not

relevant to the operation of the buildings.

lather than compare the different ventilation standards to each other, it

is more important to compare them to the ventilation rates measured in the

auildings. The ASHRAE smoking recommendation is used for these

comparisons. In Anchorage and Huron, the minimum ventilation rates when

the buildings are heated or cooled are about one-third of the smoking rate.

In fact, these measured ventilation rates are close to the ASHRAE nonsmoking rates. In all the other buildings, the lowest measured ventilation

rates are very close to, and at times lower than, the smoking ventilation

rates. Thus, all of the buildings are at times being operated at

ventilation rates which are lower than may be desirable for the

maintainance of indoor air quality. As will be discussed below, local

84
variations in air distribution may lead to ventilation rates in specific

zones which are very low.

The question of the adequacy of outside air intake is primarily an issue

during hot and cold weather when outside air intake is at a minimum. This

minimum outside air intake is supposedly assured by having a minimum

outside air damper position or by keeping a certain portion of the outside

air dampers open at all times. In other cases the outside air dampers are closed completely and it is assumed that leakage through the building

envelope will fulfill the minimum outside air requirements.

It is interesting to compare the measured ventilation rates under

conditions of minimum outside air intake to measurements of building

infiltration made with the dampers totally closed and the HVAC fans

running. These so-called infiltration rates provide a measure of the

tightness of the building shell and of any leakage in the HVAC system. The

measurements are not strictly a measure of the shell tightness because

ventilation systems are often designed to pressurize a building which will

lead to more air leakage than that induced by the weather alone. The

daytime ventilation rates during periods of minimum outside air intake and

the 0% outside air infiltration rates are compared for similar weather

conditions. This comparison provides an indication of how much additional

air is really brought in through the outside air intake to meet ventilation

requirements and how much of the outside air intake results from

uncontrolled air leakage. In Pittsfield and Springfield, the ventilation

rates are about 0.2 exchanges per hour higher during occupied periods than

the exchange rates when the building outside air dampers are closed

tightly. In Anchorage, Columbia, Fayetteville, and Norfolk the difference

is only 0.1 exchanges per hour, and in Huron and Ann Arbor the difference

is insignificant. Thus, during times of minimum outside air intake, little

of the outside air enters the Huron and Ann Arbor buildings through the

outside air intake vents. In the rest of the buildings, the amount of air

brought in through the vents is comparable to the ASHRAE nonsmoking

ventilation recommendation. Thus, either the minimum outside air damper

settings are much too low or the building designers are relying on residual

air leakage or infiltration to meet outside air ventilation requirments.

Table 6.20 shows the monthly average ventilation rates for all nine

buildings based on monthly average outside temperatures for the cities or nearby cities and an assumed inside temperature of 73°F (23 °C). The

ventilation rate for each month is based on the averages in table 6.18 or visual inspection of the plots of ventilation versus temperature difference

(figure 6.3) when the mean ventilation rate is not representative of the

data. Again there are some very low monthly average ventilation rates in some of the buildings. In some cases, the monthly average ventilation rate

is lower than the ASHRAE recommendation. Even when the monthly average is

not below the recommendation, there will be periods during the month when

the ventilation rate is lower.

6.5 Ventilation Efficiency

In measuring the ventilation rates in the eight office buildings it has

been found that when the mechanical systems are bringing in minimum amounts

of outside air, these rates are close to or below suggested ventilation

levels. In addition, these measured rates are averages over an entire

85
building, and there are local variations in ventilation and in the

uniformity of air distribution among zones, floors, rooms and parts of

rooms. These local variations lead to lower effective ventilation rates in

specific areas than for the whole building. Some of these variations are evident during the ventilation measurements after the injection of the SFg

tracer when the SFg concentration on some of the floors does not increase

at the same rate as the rest of the building. There are many ways to

define ventilation efficiency, but they generally quantify the departure

from uniform mixing of the supply air flowing into a space with the air in

that space. In addition to a floor not receiving its proper portion of

supply air flow, there can also be distribution problems on a floor.

Individual rooms may not receive the appropriate amount of supply air even

though the floor or zone is properly ventilated. This can happen when

partitions are installed in a room and obstruct the intended airflow

through the space. Finally, even within a well ventilated room the supply

air may be removed through exhaust or return ducts before it mixes with the

rest of the interior air. Occurrences of such "short-circuiting" further

reduce the effective ventilation rate in the occupied spaces of a building.

Thus, low ventilation efficiency can reduce an already low ventilation rate

to a lower effective ventilation rate for the occupants of a building. The

extent of such air distribution problems in buildings is not well known and

needs to be investigated. Tracer gas techniques can be used to study air

distribution and measure ventilation efficiency on a large scale (floors

and zones) and on a small scale (within a room).

6.6 Conclusions

The average natural air infiltration rates measured in these buildings

varied from 0.2 air changes per hour for the Huron federal building to 0.70

air changes per hour for the Ann Arbor federal building. The component of

the design heating load from these buildings ranged from 23% for the

uninsulated Fayetteville federal building to 61% for the new Springfield

federal building. In four of the buildings air infiltration contributed to

over 50% of the heating loads. Two of the federal buildings. Anchorage and

Huron, have low air infiltration rates (0.28 and 0.20 air changes per

hour). However, even for these buildings air infiltration was a very

important part of the heating load.

Ventilation rates under occupied conditions were also measured in the eight

buildings. It was found that for hot and cold outside temperatures, the

buildings are operated at minimum ventilation levels to reduce space

conditioning loads. At mild temperatures, outside air is used to cool the

buildings and the ventilation rates increase significantly. The minimum

ventilation rates show little temperature dependence in most of the

buildings, but some of the buildings exhibit a dependence on wind speed.

When the miniumum ventilation rates vary with weather conditions, this

implies that uncontrolled air leakage or weather induced infiltration is a significant portion of the net ventilation rate. In most of the buildings,

the summer and winter minimum ventilation rates are similar, but in some buildings there is a notable difference between the two minimum ventilation

rates. The minimum ventilation rates were compared to minimum outside air

intake levels suggested by ASHRAE, and it was found that most of the

buildings were operated very close to or below the ASHRAE recommendation.

Two of the buildings were operated well below this recommended ventilation

rate. Local variations in air distribution and problems of ventilation

86
efficiency can lead to effective ventilation rates in specific areas of the

building which are significantly lower than the average rate for the

building. Three of the buildings, Springfield, Ann Arbor and Columbia, had

minimum ventilation rates from 20 to 50% more than required, thus wasting

energy during periods of extreme weather.

87
Table 6.18 Average Ventilation Rates in the Buildings

Temp

°F

Diff

(°c ) Anchorage Ann Arbor Columbia Fayettevil le

-18,-9 (-10,-5) — .

0.68/0.18

-9,0 (-5,0) — — 0 . 68 / 0.21 0.36/0.12

0,9 (0,5) — 0.94/0.95 0.69/0.32 0.65/0.39

9,18 (5,10) 1.34/0.36 1.94/0.42 1.10/0.90 0.35/0.07

18,27 (10,15) 1.22/0.25 1.96/0.97 1.09/0.56 0.35/0.01

27,36 (15,20) 1.10/0.23 0 . 86 / 0.20 0.64/0.26 0.32/0.02

36,45 (20,25) — 0.47/0.07 0.62/0.24 —

45,54 (25,30) 0.46/0.14 — — —

54,63 (30,35) 0.24/0.04 — -- —

63,72 (35,40) 0.36/0.10 -- — —

72,81 (40,45) 0.26/0.02 —

-- —

Temp

oF

Diff

(°c)

Huron /SB*Mean ** Norfolk Pittsfield Springfield

-27,-18 (-15,-10) . 0.73/0.09 —

—

-18,-9 (-10,-5) 0.19/0.00 0.62/0.11 0.49/0.09 0.55/0.09

-9,0 (-5,0) 0.16/0.04 0.58/0.07 0.43/0.09 —

0,9 (0,5) 0.53/0.43 0,75/0.19 1.19/0.73 0.59/0.08

9,18 (5,10) 0.52/0.00 1.00/0.32 1.25/1.15 0.62/0.08

18,27 (10,15) 0.13/0.04 1.05/0.37 0.67/0.48 0.76/0.20

27,36 (15,20) 0.14/0.06 0.84/0.47 0.96/0.20

36,45 (20,25) 0.32/0.14 0.70/0.09 0.38/0.14 0.95/0.22

45,54 (25,30) 0.25/0.05 0.66/0.06 — —

54,63 (30,35) 0.26/0.07 -- -- —

63,72 (35,40) 0.29/0.04 — ~ —

72,81 (40,45) 0.31/0.06 — — —

All the ventilation rates are in units of exchanges per hour.

* Calculations neglect some very high, wind induced

ventilation rates.

** Standard deviation of the mean ventilation rate.

88
Table 6.19 Recommended Minimum Ventilation Rates in the Buildings

Measured

Building 10% Total Air ASHRAE

Smoking

62-81

Non

Smoking

Measured

Building

Min imum

Minimum as Percent of

Requirement*

Anchorage 0.28 0.67 0.17 0.26 39%

Ann Arbor 0.36 0.38 0.09 0.47 124%

Columbia 0.28 0.41 0.10 0.62 151%

Fayetteville 0.57 0.41 0.10 0.32 78%

Huron 0.31 0.49 0.12 0.13 26%

Norfolk 0.25 0.69 0.17 0.62 90%

Pittsfield 0.32 0.42 0.10 0.38 90%

Springfield 0.44 0.46 0.12 0.55 120%

All the ventilation rates are in units of exchanges per hour.

* Based on ASHRAE 62-81 smoking requirement

89
Table 6.20 Monthly Average Ventilation Rates

Month Anchorage^

O Ann Arbor Columbia Fayetteville^

January 0.46 0.47 0.64 0.32

February 0.46 0.47 1.09 0.32

March 0.46 0.47 1.09 0.35

April 0.75 1.96 1.10 0.35

May 1.10 1.94 0.69 0.65

June 1.22 0.94 0.68 0.36

July 1.22 0.50 0.68 0.36

August 1.22 0.50 0.68 0.36

September 1.22 1.94 0.68 0.36

October 0.75 1.96 1.10 0.35

November 0.46 0.86 1.09 0.35

December 0.46 0.47 0.64 0.32

Huron Norfolk Pittsfield^ Springf ie Id

January 0.26 0.70 0.40 1.00

February 0.26 0.70 0.40 1.00

March 0.32 1.05 0.38 0.95

April 0.14 1.00 0.67 0.76

May 0.52 0.75 1.25 0.62

June 0.53 0.58 0.50 0.59

July 0.16 0.58 0.50 0.59

August 0.53 0.58 1.19 0.59

September 0.52 0.75 1.25 0.62

October 0.13 1.00 0.67 0.76

November 0.32 1.05 0.84 0.96

December 0.26 0.70 0.40 1.00

All the ventilation rates are in units of exchanges per hour.

1 Based on outside temperatures from Homer, AK.

2 Based on an average of outside temperatures from Flint and

Detroit, MI.

3 Based on outside temperatures from Ft. Smith, AR.

4 Based on outside temperatures from Hartford, CT.

90
VENTILATION

RATE

(hr

ANCHORAGE: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F)

0 20 40 60 80

ANN ARBOR: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) 0 10 20 30 40 50

COLUMBIA: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) -20 -10 0 10 20 30 40 FAYETTEVILLE: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) 0 10 20 30

TEMPERATURE DIFFERENCE (*C)

Figure 6.3 Ventilation Rate Versus Temperature Difference

91
HURON: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) -20 0 20 40 60 80

TEMPERATURE DIFFERENCE ( C C)

NORFOLK: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

TEMPERATURE DIFFERENCE (°F) -20 0 20 40 60

TEMPERATURE DIFFERENCE (°C)

PITTSFIELD: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

-10

TEMPERATURE DIFFERENCE (°F) 0 10 20 30 40

SPRINGFIELD: OCCUPIED VENTILATION RATE vs TEMPERATURE DIFFERENCE

-10 TEMPERATURE DIFFERENCE (°F) 10 20 30 40 50

Figure 6.3 (continued) Ventilation Rate Versus Temperature Difference

92
VENTAATtON

RATE

(HR 1

ANN ARBOR OCCUPIED VENTILATION RATE VS. WIND SPEED

[(AT: 11.1 to 13.9°F (20 to 25°C)]

AflND SPEED (mph) HURON: OCCUPIED VENTILATION RATE vs WIND SPEED

[AT: 11.1 to 13.9°F (20 to 25°C)]

WIND SPEED (mph)

0 2 4 6 8

HURON: OCCUPIED VENTILATION RATE VS. WIND SPEED

[AT: 13.9 to 16.7 °F (25 to 30°C)]

WIND SPEED (mph) 0 2 4 6 8 10 12 14

Figure 6.4 Ventilation Rate Versus Wind Speed

93
7. Building Tightness Testing Using Pressurization

7.1 Introduction

Whole building pressurization testing has been used for many years to

evaluate the airtightness of single-family homes [13,14]. In this test

method, a fan induces a large and uniform pressure difference across the

building envelope, and the airflow rate required to induce a specific

pressure difference between inside and outside serves as a measure of the

airtightness of the building shell. Although the test conditions differ

considerably from those which normally induce air exchange, pressurization

testing provides a quick and quantitative measurement of building

tightness. The technique has been used to evaluate the airtightness of a small number of large buildings [15,16], Most of the previous

pressurization measurements on large buildings involved bringing a high

capacity fan to the building, as is done on a smaller scale for homes. The

tests described below differ in that the existing HVAC equipment was used

to pressure test the buildings. These tests employed a constant injection,

tracer gas measurement technique to measure the airflow rate required to

induce each inside-outside pressure difference. Seven of the eight federal

buildings were subjected to whole building pressurization tests.

Pressurization testing was also applied to individual windows to evaluate

the airtightness of these components [17].

7.2 Test Methods

The buildings were pressure tested in a manner similar to that used in

houses [7]. A large airflow into the building induced a large and constant

pressure difference across the building envelope. Several different

pressure differences were induced and the flow required to induce each

pressure difference was measured. During the whole building pressurization

tests the building ventilation system was arranged as shown in figure 7.1.

The supply fans were operating while all return and exhaust fans were

turned off. All return dampers were closed so that the supply air flowing

into the building could only leave the interior through outside doors,

windows and other leakage sites. The airflow through the supply fans was measured using a constant flow, tracer gas injection scheme [18], Tracer

gas (sulfur hexafluoride, SF 5

) was injected at a constant and known rate

into the airstream being brought into the building at a location close to

the outside air intake vent. The tracer gas concentration was measured in

the supply duct downstream from the injection point. Under conditions of

good mixing of the tracer with the airflow, the flow rate can be determined

from the SF^ injection rate and the measured concentration according to

Q

= i/c , (7.1)

where

Q

= airflow rate

i = tracer gas injection rate

c = tracer gas concentration.

The airflow rate Q into the building was modulated either by adjusting the

outside air intake dampers or the intake vanes on the centrifugal supply

fans. In buildings with more than one large supply fan, individual fans

94
could be turned on or off to further adjust the flow. For each induced

flow rate Q, the inside-outside pressure difference was measured at several

locations as discussed below. All of the pressurization tests were

conducted under relatively mild wind speed conditions (less than 4.5 mph (2

m/s)) and at outside temperatures between 50 and 68 °F (10 and 20°C) in

order to avoid weather induced pressure differences during the tests.

The component pressurization tests were conducted by measuring the airflow

necessary to induce pressure differences across individual components [17].

A temporary enclosure was installed around the component being tested, from

inside the building, and air was blown into this enclosure such that it

could only leave through leaks in the window being tested. The airflow was induced with a large vacuum cleaner and measured with an electronic

flowmeter. The airflow rate was modulated by diverting varying amounts of

airflow out of the vacuum cleaner at a point upstream of the flowmeter.

7.3 Test Equipment

The equipment used in the whole building pressurization measurements

includes flowmeters to measure the SFg injection rate, an electron capture

detector gas chromatograph to determine the SFg concentration and magnetic

linkage pressure gauges to determine the inside-outside pressure

difference. The SFg flowmeters were variable-area float-type rotameters

equipped with a control valve to adjust the SFg injection rate. Each

flowmeter was individually calibrated for SFg by the manufacturer with an accuracy of +. 1% of full scale. The SF 5 concentration downstream of the

injection was measured with the same system used in the tracer gas

measurements of air infiltration rates of these buildings. The gas

chromatograph/electron capture detector was calibrated with +. 5% in the

range of 10 to 250 ppb. The inside-outside pressure differences induced

during the pressurization tests were measured with magnetic linkage

pressure gauges which were individually calibrated against an inclined

manometer. The pressure gauges were accurate within roughly +_ 0.0025 in

H2 O (0*6 Pa). The induced pressure difference across the building shell

was measured at several locations in each building. The same pressure

gauges were used in the pressure tests of individual components. The

flowmeters used in these tests were electronic devices utilizing hot-wire

amemometer principles, with an accuracy of +. 2%.

7.4 Details of Whole Building Pressurization

The following section briefly outlines the details of the whole building

pressurization measurement in each building, including location and number

of pressure difference measurements, fan operation and pressure differences

achieved.

Anchorage

The federal building in Anchorage is divided into six connected modules.

The modules vary in height from two to six stories. The building has six

supply fans of varying capacities, one for each module. All of the modules

are open to each other, and the airflow from any of the six fan 6 pressurizes the entire building. All six fans were used in the

pressurization tests, and therefore SF^ was injected in, and sampled from,

six locations in the building. Four different inside-outside pressure

95
differences were induced in this building, ranging from 0.055 to 0.150 in

(14 to 38 Pa). For the lowest pressure difference, only four of the

six fans were operated. The next highest pressure difference employed five

of the fans, and the other pressure differences were obtained using all six

fan. The pressure differences were measured at two ends of the building on the ground floor, and at the fifth floor of one of the modules. The

variation in pressure difference among these three locations was only +_ 0.004 in H2 O (1 Pa).

Ann Arbor

The federal building in Ann Arbor is a four story building with a terraced

roof construction, i.e. each story has less floor area than the story

below. There is a post office in part of the lower two floors which has

its own air handling system. The lobby also has a separate air handler.

The rest of the building is served by a main air handler located on the

third floor. This building was pressurized using only the main supply fan.

Four inside-outside pressure differences were induced, ranging from about

0.040 to 0.240 in H 2 O (10 to 60 Pa). The pressure differences were

measured at two locations on the ground floor and on the third floor. The

post office on the first floor, which occupies about 16% of the total

building volume, is not served by the fan used in the pressurization test.

Although there is not a great deal of communication between the main

building volume and the post office, a significant pressure difference did

develop between the post office and the outside during these tests. The

post office-outside pressure difference was about one-half of the main

volume-outside pressure difference. In analyzing the test data the total

building volume (including the post office) was assumed to be involved in

the test.

Columbia

The federal building in Columbia is a fifteen story building. It also has

a two story courthouse attached through an underground passageway, but only

the fifteen story tower was pressure tested. The building has two large

air handling systems located in a mechanical room on the fifteenth floor.

The first floor, basement and lobby are served by two air handlers located

in the basement. Although, there are two large fans in this building, only

one fan running at partial capacity was needed to induce inside-outside

pressures from 0,104 to 0.240 in H 2 ® (17 to 50 Pa). The pressure

difference was measured at the odd numbered floors from three to thirteen.

Huron

The federal building in Huron is a four story building. There are two main

supply fans in a mechanical penthouse serving two zones which communicate

freely. Both fans were used to pressurize the building for some of the

data points, and only one for the others. The induced pressure differences

ranged from 0.068 to 0.200 in H2 O (17 to 50 Pa) and were measured at two

locations on each of the four floors.

Norfolk

The Norfolk federal building is an eight story building. The building has one large supply fan in the mechanical penthouse which was sufficient to

96
induce inside-outside pressure differences from 0.032 to 0.120 in H2O (8 to

30 Pa). These pressure differences were measured on each floor of the

building

.

Pittsfield

This two story building has a separate fan for each story. The locations

for communication between the floors include two stairways, an elevator

shaft and other smaller leakage sites. Using both fans, identical insideoutside pressure differences were developed on each floor. These pressure

differences were measured at two locations on each floor and ranged from

0.100 in H 2 0 (25 Pa) to almost 0.400 in H 2 0 (100 Pa).

Springfield

The Springfield federal building is a five story building. There are two

large supply fans located in a penthouse which serve the north and south

zones respectively. On the upper floors, the two zones are connected

through passageways. On the first two floors, both zones open onto an atrium. During the pressurization test all doors between the zones and

into the atrium were open. The north zone fan was used to obtain pressure

differences of 0.040 and 0.056 in H 2 O (10 and 14 Pa), while both fans were

used to induce a 0.092 in H2 0 (23 Pa) pressure difference. The insideoutside pressure differences were measured on all five floors of the north

zone, and on the second and fourth floors of the south zone.

7.5 Whole Building Pressurization Results

The following section presents the results of the pressurization tests on the seven federal buildings and some analysis of these data. In addition,

the airtightness values of these buildings are compared to measurements

made in several Canadian office buildings.

The test data for each building is in the form of several combinations of

airflow Q and inside-outside pressure difference Ap. For each building,

the Q and Ap values are fit to a curve of the form

Q

= CA pn (7.2)

Table 7.1 presents equations for the curve fits for each of the seven

buildings and the range of pressure differences which were achieved. Five

of the seven exponents n are, as expected, in the approximate range of one- half to one. The exponent for Springfield is quite large due to

difficulties in maintaining the low flow rates at a constant level, however

the flow at 0.092 in H

2 O (23 Pa) was repeatable and is believed to be

accurate. There are many ways to quantify the results of pressurization

tests. The test results for homes are often presented in terms of the

induced flow rate at an inside-outside pressure difference 0.20 H 2 ° (50

Pa). The ranges of measured pressure difference in table 7.1 are variable

over the seven buildings, but they all have measurements at roughly 0.10 in H 2 0 (25 Pa). In addition, the measurements close to 0.10 in H 2 O (25 Pa)

were repeatable in the buildings which had flow exponents out of the range

from one-half to one. Therefore, the flow at 0.10 in H

2 o (25 Pa) at. determined with equation 7.2 is used to compare the tightness of these

buildings. By using the 0.10 in H2O (25 Pa) flow rates we need not compare

97
values extrapolated out of the range of measurements.

The 0.10 in H

2 O (25 Pa) flow rates in units of building volumes or exchanges per hour and cfm per ft 2 (mr/hr per m

2

) of building envelope

(wall and roof) area are presented in table 7.2. Note that these flow

rates are significantly larger than the infiltration rates induced by

weather. The 0.20 in H

2O (50 Pa) exchange rates of the buildings are about

1.5 times the 0.10 in H2O (25 Pa) flows shown in the table (assuming n=0.65

in equation 7.2), and are low compared to those measured in homes. U.S.

homes generally range from about 5 exchanges per hour to greater than 20

exchanges per hour at 0.20 in H 2 0 (50 Pa). Swedish and Canadian homes are

being built with 0.20 in H2 O (50 Pa) flow rates of less than 2 exchanges

per hour [19]. Thus, the 0.20 H

2 0 (50 Pa) flow rates of these federal

buildings correspond to very tight houses.

In comparing the pressurization test results of the federal buildings to

each other and to residential buildings, the important factor of surface to

volume ratio arises. Figure 7.2 shows the surface to volume ratios S/V in

ft 2 /ft^ (m^/m^) for the federal buildings and two sample houses. The 1-

story house is assumed to have a 1200 ft 2 (110 m

2

) square floor area and 8

ft (2.5 m) ceilings. The 2-story home also has a square floor plan with

roughly 1100 ft 2 (100 m2

) on each floor and a 16 ft (5 m) building height.

It is seen in the figure that the large sizes of the federal buildings lead

to values of S/V which are about one-third of those associated with homes.

Figure 7.3 shows the 0.10 in H 2 0 ( 25 Pa ) flows listed in table 7.2. The

vertical scale on the left shows the 0.10 in H2 O (25 Pa) flows in exchanges

per hour for the seven federal buildings and the two sample houses shown in

figure 7.2 (2.0 exchanges per hour at 0.20 in H2 O (50 Pa) very tight). The

vertical scale on the right shows the 0.10 in H2 O (25 Pa) flows in cfm/ft

(m^/hr-m 2

) of envelope area. In moving from exchanges per hour to cfm/ft2

(m^/hr-m2

) the ranking of the buildings^ tightness changes significantly.

Also, the spread in the leakage values using the second measure is larger

than the spread in exchanges per hour. The most significant change occurs for the sample houses which are almost the tightest in terms of cfm/ft 2

(m^/hr-m2

) of envelope area. Thus, while the federal buildings appear to

be quite tight in terms of exchanges per hour compared to houses, the

airtightness per unit of envelope area is not as impressive.

The airtightness of the federal buildings in units of cfm/ft 2 (m^/hr-m2

) is

worse if one considers the fact that the roofs are of low-slope built-up

design, constructed to be impervious to both water and air. Therefore, it

might be more appropriate to normalize the 0.10 in H2O (25 Pa) flows by the

wall area alone instead of using the total envelope area including the

roof. Normalizing the leakage rate with the wall area will lead to higher

values of the 0.10 in H

2Q (25 Pa) flows in cfm/ft 2 (m3 /hr-m2

).

These values of induced flow per unit envelope area may be compared to

values obtained previously in Canada [15,20]. In the Canadian work,

building leakage coefficients were determined for eight office buildings

with construction dates ranging from 1964 to 1974 and heights from 9 to 25

storys. Seven of the eight Canadian buildings ranged from 0.13 to 0.34

cfm/ft 2 (2.4 to 6.2 m^/hr-m2

) at 0.10 in H2 0 (25 Pa) and one had a value of

0.60 cfm/ft2 (11.0 m^/hr-m2

). These Canadian values are flows per square

meter of wall area as opposed to envelope area as used in table 7.2.

98
Comparing these values to those listed in table 7.2, we see that the

federal buildings are comparable in tightness to these Canadian buildings.

7.6 Component Pressurization Results

Windows were individually pressure tested in six of the eight buildings.

Because of the large variation in component size and frame arrangements, it was difficult to seal the test apparatus. For these reasons, only a small

number of components were tested and the results should be considered

preliminary. The results are expressed in units of cfm (L/s) of induced

airflow at 0.30 in H 2 0 (75 Pa) per foot (meter) of crack length for

windows, and include both frame and sash leakage. The ASHRAE Handbook of

Fundamentals [8] lists a window leakage standard of 0.50 cfm/ft (0.77 L/sm) (sash leakage only), varying somewhat with window type. Table 7.3 shows

the results of the window pressurization tests for the six buildings

tested. In addition, this table lists samples of window leakage

measurements from the literature [15,21,22].

In table 7.3 there is a wide variation in the measured window leakage

rates, even for the relatively small number of windows tested. The

operable windows in the Columbia building are very leaky, along with some cracks around windows in the Fayetteville building through which daylight

is visible. Most of the other windows tested are somewhat leakier than the

standard of 0.50 cfm/ft (0.77 L/s-m). As mentioned earlier, the standard

applies to sash leakage only, while these measurements include both sash

and frame leakage. The field tests of many new residential windows yielded

an average value very close to this standard [21], The office building

from reference 16, built in the mid-1960's, has very leaky windows.

Several windows from Canadian supermarkets and shopping centers [17] had

leakage values comparable to those in the office buildings discussed in

this report. Most of the windows tested in the federal buildings and those

in the literature are leakier than the 0.50 cfm/ft (0.77 L/s-m) standard.

Window leakage rates can be combined with the total window crack length to

estimate the net window leakage in the buildings. These window leakage

values are compared with the total building leakage from the whole building

pressurization tests to determine the fraction of total building leakage

associated with windows. This fraction is generally around 20% for houses

[23]. Since only a small number of windows were tested in the buildings,

the measured leakage values may not be representative of the building

average. Therefore, in calculating the fraction of building leakage

associated with windows, the standard of 0.50 cfm/ft (0.77 L/s-m) is used

along with two and three times this value. In addition, the average of the

measured values is used when available. Table 7.4 presents the results of

these calculations of the fraction of total building leakage attributable

to windows at 0.10 in H

2 O (25 Pa). The total building leakage is based on the equations in table 7.1. Although it is not entirely clear as to which

window leakage value is appropriate for each building, the windows account

for about 10 to 20% of the total building leakage at 0.10 in H 2 O (25 Pa).

This percentage is similar to the fraction of leakage associated with

windows in homes.

99
7.7 Relation of Pressurization Test Results to Infiltration Rates

While the pressurization tests are useful for comparing buildings to each

other and to airtightness standards, the question remains of how the

pressurization test results are related to air infiltration rates induced

by weather. This question has been studied extensively in houses [23], and

less so in large buildings [24,25]. The existence of both whole building

pressurization test results and air infiltration measurement for the seven

federal buildings allows a comparison of the two measurements. Figure 7.4

is a plot which compares tracer gas measurements of infiltration rates in

the buildings to the 0.10 in H2 O (25 Pa) flow rates in exchanges per hour

from the pressurization tests. The infiltration rates are measurements of

the leakage induced by weather, and the rates for each building correspond

to approximately the same weather conditions. The correlation between

these two variables is as strong as it is for homes, but the slope of the

infiltration rate versus pressurization flow is steeper for these large

buildings than it is for houses. Such a simple relation between

pressurization and infiltration neglects the dependence of infiltration on weather conditions. A more complex model of the

pressurization/ inf iltration relation in large buildings which accounts for

weather effects is discussed below.

Shaw and Tamura, of the National Research Council of Canada, have developed

a model which predicts infiltration in large buildings [24]. This model

consists of predictive equations for infiltration based on a computer model

building and wind tunnel tests of a model of a 40-story building. The

buildings considered in the work of Shaw and Tamura are generally taller

than the federal buildings discussed in the report.

This large building model has separate predictive equations for wind and

temperature induced infiltration. The wind induced infiltration Qw

is

expressed as

Qw

= aC'LH(pu2C

p

/2) n (7.3)

where is a factor to account for wind directions other than normal to the

longest building wall, which is of length L. H is the building height. C'

and n are the building flow coefficient and exponent from equation 7.2.

The value of C' is the leakage coefficient of the walls, determined by

dividing the value of C in equation 7.2 by the building wall area, p is

the air density, u is the wind speed in m/ s and C^ is the wind pressure

coefficient for the windward wall. The stack induced infiltration is

expressed as

Q s = C'S[3464 y (AT/TinTout )] n [ (3H) n+1 /n+l] (7.4)

where S is the building perimeter and AT is the inside-outside temperature

difference in °C. 3 is the height of the neutral pressure level divided by

the building height. Y is a thermal draft coefficient which accounts for

the extent of vertical communication in the building. A value of Y = 0.0

corresponds to no openings between floors and Y = 1.0 corresponds to a totally open interior. While there is no straightforward technique for

determining the appropriate value of Y for an individual building, Shaw and

Tamura suggest a value of 0.80 for office buildings, and this value was

used for all the federal buildings with two exceptions. In Anchorage, all

100
the floors open onto a central lobby area, and therefore a value of 0.95

was used for the thermal draft coefficient. The Springfield building has a vertically open atrium on the front of the building and a value of 0.87 was

used. The neutral pressure level is assumed to equal one-half the building

height in all the buildings. The wind Qwand temperature difference Q s infiltration rates are combined to yield and net infiltration rate

according to

Qws = max(Qw ,Q g

) [1 + 0.24( (min(Qw ,Qs )/max(Qw ,Qs) ) 3,3

] (7.5)

The max and min functions correspond to the maximum or minimum value in the

parentheses

.

Table 7.5 compares the measurements of infiltration in the seven buildings

to predicted rates from the Shaw-Tamura model. The predictions are made

for the same weather conditions as the measurements, a wind speed of 4.5

mph (2 m/s) and an outside temperature of 45°F (7°C). In all buildings,

the predictions are much lower than the measurements, especially in Ann

Arbor and Springfield. The Springfield predictions are low because the

curve fit to the building's pressurization data (equation 7.2) has a large

value for the flow exponent (n=2.09) and a correspondingly low value for

the flow coefficient. This low flow coefficient value leads to low

predicted infiltration rates. If instead the exponent is assumed to be

equal to 0.65 and the 0.10 in 1^0 (25 Pa) flow rate is used to get a new

flow coefficient, these predictions are more accurate. These second

Springfield predictions correspond to the Springfield-adjusted values in

table 7.5. This result of generally low predictions compared to

measurements was also found by Hunt and Treado [25] in an eleven-story

office building. They attributed the larger measured infiltration rates to

toilet exhausts and other forced ventilation. However, in the seven

federal buildings discussed here, all mechanical exhausts were off during

the infiltration measurements.

It is not clear why the predicted infiltration rates are generally so much

lower than the measurements. One potential explanation for the

disagreement is the existence of open elevator shafts in the buildings,

that are quite susceptible to stack induced infiltration. Another reason may have to do with the fact that during the infiltration measurement the

HVAC system was running to keep the interior air well mixed. Even though

the outside air supply and exhaust dampers were closed, they could have

leaked. However, in Anchorage and Pittsfield, infiltration measurements

were made with these dampers sealed with plastic sheets, and the measured

rates were no different from the rates when the dampers were closed but not

sealed. Another factor to consider is leakage due to local pressurization

when the fans are running. All the buildings use ceiling plenums as return

ducts, and leakage in the outside walls surrounding this plenum space will

lead to the intake of outside air through these leaks and increased air

exchange rates. Such plenum leaks were seen in Fayetteville and their

existence is suspected in other buildings. However, it is difficult to

estimate the contribution of such leakage to the net air exchange of the

building. Another reason for the disagreement between the model

predictions and the measurements may be that the model was developed for

taller buildings (about 40-stories) than the federal buildings (from two to

fifteen-stories). Another factor could be that the wind speed measurements

101
at the federal buildings were made roughly 16 ft (5 m) above the roof while

the model calls for free stream wind speed at the building height.

However, predicted infiltration rates for higher wind speeds do not exhibit

significantly larger errors than the 4.5 mph (2 m/s) predictions shown in

table 7.5, and therefore wind speed measurement error does not appear a likely source of the model error.

7.8 Conclusions

As part of this project to evaluate the thermal integrity of the building

envelopes of eight federal buildings, the airtightness of the envelopes

were evaluated using pressurization techniques. Seven of the buildings

were subjected to whole building pressurization tests and were found to

possess airtightness levels similar to tight houses in units of exchanges

per hour at an induced pressure difference. The airtightness of the

buildings in units of flow per envelope area were generally higher than for

tight houses due to the low surface to volume ratios of the federal

buildings. Therefore, the airtightness in exchanges per hour from the

pressurization tests provides a misleading indication of the federal

buildings' airtightness. A small number of windows in six of the buildings

were pressure tested individually, and while a wide range of leakiness

levels was evident, they were generally leakier than a common window

tightness standard. The fraction of total building leakage associated with

windows was calculated to be about 10 to 20%, a percentage similar to that

found in houses. The large building infiltration model of Shaw and Tamura

was applied to the seven buildings which were pressure tested, and the

predictions were lower than the infiltration rates measured with tracer

gas.

102
Table 7.1

Curve Fits to Pressurization Data

and Pressure Measurement Range

Range of Measured

Building Curve Fit Pressure Difference

Q(cfm) (Q(m3 /hr))

Ap(in H2 O) (Ap(Pa)) in H2 O (Pa)

Anchorage Q

vs 3.66x10"* Ap- 61

(Q - 2.14xl0 4 A p* 61

) .056-. 152 (14-38)

Ann Arbor Q

= 7.54x104 A p* 67

(Q = 3. 17xl03

A p* 67

) .044-. 244 (11-61)

Columbia Q

= 1.44x10-* Ap* 47

(Q - 1.83xl04 Ap* 47

) .104-. 240 (26-60)

Huron Q

= 3. 18xl04 Ap’ 64 (Q = 1.58xl03 Ap- 64

) .068-. 200 (17-50)

Norfolk Q

= 2.83xl0 5 Ap* 74

(Q - 8.08xl03 A p

- 74

) .032-. 120 (8-30)

Pittsfield Q

= l.lOxlO4 Ap- 36

(Q " 2.55xl03 A

p

- 36

) . i—* 00 1 .

LO OO OO (25-97)

Springfield Q

= 5.99x10** Ap2 - 09

(Q = 9.90X10 1 Ap 2 -® 9

) .040-. 092 (10-23)

103
Table 7.2

Pressurization Test Results in Terms of 0.10 in H2O Flow Rates

Building

Air 1 row (volumes /hr) race ac u.iu in

cfm/f t^

of envelope

tlow v 4J ra;

area

Anchorage 0.80 0.37 6.7

Ann Arbor 0.86 0.23 4.1

Columbia 0.67 0.33 6.0

Huron 0.45 0.10 1.9

Norfolk 1.45 0.40 7.2

Pittsfield 0.95 0.19 3.5

Springfield 1.43 0.51 9.2

104
Table 7.3

Results of Window Pressurization Tests

Building Window

Air Flow Rates at 0.3 in H2 0 (cfm/ft)

(L/s-m)

Anchorage Inoperable 2.08, 0.43, 0.70, 0.57, 0.63

(3.22, 0.67, 1.09, 0.89, 0.98)

Ann Arbor Inoperable 0.59, 0.67

(0.91, 1.04)

Columbia Operable 2.85, 3.59, 2.33, 2.08

(4.41, 5.56, 3.61, 3.22)

Fayetteville Inoperable

Window Cracks*

0.28, 0.21

(0.44, 0.32)

4.78, 3.85

(7.40, 5.96)

Norfolk Inoperable 0.79, 1.01, 0.95

(1.23, 1.56, 1.47)

Pittsf ield Operable 0.84, 0.26

(1.30, 0.41)

Window Leakage Standard

(Ref. 8)

0.50

(0.77)

Residential Windows

(Ref 21)

Mean Value of 0.52

(0.81)

Office Building

(Ref. 22)

0.88, 2.29, 2.29, 2.30, 2.67, 3.21,

3.28, 6.98, 7.71, 10.36

(1.36, 3.54, 3.55, 3.56, 4.13, 4.97,

5.08, 10.81, 11.94, 16.04)

Supermarkets and Shopping

Malls (Ref. 15)

0.13, 0.13, 0.36, 0.39, 0.71, 0.77,

1.55

(0.20, 0.20, 0.55, 0.60, 1.10, 1.20,

2.40)

*These are cracks around particularly leaky windows.

105
Table 7.4

Fraction of Total Building Leakage Associated with Windows

Window Leakage at

0.10 in H2 0 (25 Pa)* Fraction of Building Leakage

Building cfm/ ft^ (L/s-m) Associated with Windows

Anchorage 0.23 (0.36) 8.8%

0.46 (0.72) 17.6%

0.70 (1.08) 26.4%

Measured** 0.36 (0.55) 13.4%

Ann Arbor 0.23 (0.36) 6.2%

0.46 (0.72) 12.4%

0.70 (1.08) 18.6%

Measured 0.34 (0.53) 9.1%

Columbia 0.23 (0.36) 6.4%

0.46 (0.72) 12.8%

0.70 (1.08) 19.2%

Measured 1.12 (1.74) 30.9%

Huron 0.23 (0.36) 13.3%

0.46 (0.72) 26.6%

0.70 (1.08) 39.9%

Norfolk 0.23 (0.36) 6.4%

0.46 (0.72) 12.8%

0.70 (1.08) 19.2%

Measured 0.44 (0.68) 12.1%

Pittsfield 0.23 (0.36) 8.3%

0.46 (0.72) 16.6%

0.70 (1.08) 24.9%

Measured 0.28 (0.43) 10.0%

Springfield 0.23 (0.36) 7.1%

0.46 (0.72) 14.2%

0.70 (1.08) 21.3%

*0.23, 0.46 and 0.70 c fm/ft^ (0.36, 0.72 and 1.08 L/s-m) correspond to 1 and 3 times the standard of 0.50 c fm/ft^ at 0.3 H2O (0.77 L/s-m at 75 P

**This value is the average for all the windows tested in this building.

106
Table 7.5

Predictions of the Shaw-Tamura Large Building Model

Measured Infiltration* Predicted Infiltration

(exchanges /hour) (exchanges /hour)

Wind Speed <4.5 mph (2 m/s) u=4.5 mph (2 m/s)

Building Tout ~ 45° F (7 °C) Tout = 45°F

Anchorage 0.25 0.07

Ann Arbor 0.55 0.02

Columbia 0.35 0.13

Huron 0.15 0.03

Norfolk 0.50 0.15

Pittsfield 0.35 0.14

Springfield 0.40 0.01

Springfield-Adjusted 0.25

*Representative infiltration rate for specified weather conditions.

107
Figure 7.1

Building Pressurization Testing Set-Dp

Return

damper

Exhaust

damper

t

Return

fan

Fresh air

damper

Tracer

gas

injection —

4

Supply

fan

t?

Floor

^—return

K dampers

Floor ^

supply *-%

dampers

IOpen

damper

^^-Closed

damper

PRESSURIZATION

TEST CONDITIONS

Return fan - off

Supply fan - on

Return dampers - closed

Exhaust damper - closed

Fresh air damper - open

Floor supply dampers - open

— Tracer gas

concentration

u measurement

108
SURFACE TO VOLUME RATIO

(ft 2/ft 3

) (m2 /m3

)

0.3-

0.2 -

0.1 -

0 J

1 . 0 -

0.5-

1 -story house

• 2-story house

.Pittsfield Huron ^Fayetteville Ann Arbor -^Norfolk

. Springfield

' VAnchorage

Columbia

— * 0.2

AT

IS PASCAL

OF WALL AREA OF WALL AREA

AT 25 PASCAL ATO.IMM,0

Figure 7.2 Surface to Volume Ratios

of Federal Buildings and

Houses

Figure 7.3 Pressurization

Test Results

«

UJ»-<

ocz

o

0.5 -

0.4 -

i

-J £

U. «

UJ ® a o 3 x

(O ® < w

UJ

1 0.3 -

0.2

u.O

UJo

z<

IT

0.1

Ann Arbor

Springfield

Columbia

Anchorage

Norfolk

Pittsfield

Huron

J I I I I I L

Wind speed < 4.5 mph (2 m/s)

Outside temperature: 41-50*F

(5-10*0

_l I I I I I I I 0 0.5 1.0 1.5 PRESSURIZATION FLOW RATE AT 0.1 in H 2 0 (25 PA)

(exchanges /hr)

Figure 7.4 Weather Induced Infiltration Rates versus

Pressurization Test Results

109
8.0 Measurement of the Thermal Resistance of the Buildings

8.1 Introduction

The in-situ measurements of the thermal resistance of sections of the

building envelope were carried out between February and May of 1983 on seven of the eight federal buildings. These tests were performed using

either heat flow meters or a portable calorimeter. It was also intended to use the Envelope Thermal Testing Unit (ETTU) developed by Lawrence Berkeley

Laboratories, however, this device was not available to NBS in time for

this demonstration.

8.2 Instrumentation and Procedures

The rates of heat flow through the building envelopes and major building

components were measured with heat flow meters and a portable calorimeter.

The heat flow meter used consisted of a 4-inch (102 mm) diameter, thin,

circular, wafer-type sensor comprising the hot and cold junctions of an embedded thermopile attached to its flat surfaces. The voltage signals

generated by the heat flow meter when exposed to a thermal field were

proportional to the rate of heat flow through the meter.

Upon completion of a series of field tests, the heat flow meters were

calibrated using a standard guarded hot plate apparatus described in

references [26, 27]. The sensitivity of each heat flow meter was

determined by exposing it to a range of uniform heat flux, at the

temperature levels experienced during the field testing, after it had been

placed between the insulations attached to the hot and cold plates of the

apparatus. The accuracy of the calibration of the heat flowmeters was

about +_ 1%.

During field measurements, the heat flowmeters were taped on the inside

surfaces of the exterior walls, structural columns and beams, and the roof

deck and floor assemblies. A metal stud finder was used during the

installation of the heat flow meters to ensure that the transducers were mounted over thermal insulation filled cavities between wall framing

members

.

In order to evaluate the thermal integrity of building envelopes of the

selected office buildings, a portable calorimeter similar to that used by

Brown and Schuyler [28, 29] was designed, fabricated and instrumented for

field measurements of heat fluxes through the wall structures. The

usefulness of portable calorimeters has been demonstrated by the Division

of Building Research, National Research Council of Canada, in determining

the effects of framing members on the overall thermal resistance and heat

flow through frame walls of single-family dwellings [28, 29].

The calorimeter was a five sided box, 49x78x8 inches (1.24x1.98x0.2 m)

deep, whose open face was attached to the interior wall surface to be

measured. The calorimeter walls were constructed of two 2 inch (50 mm)

thick layers of foil-faced, semi-rigid glass fiber insulation boards glued

together with the foiled side exposed. The combined thermal resistance of

the calorimeter walls was R 17.4 ft -h-°F/Btu (3.06 m^-K/W). All joints

were staggered, filled with crumbs of glass fiber insulation mixed with

glue, and covered with aluminum foil duct tape. The calorimeter box was

110
stiffened by framing its sides and corners with a 0.5 in. (13 mm) fir

plywood board. A narrow rubber foam strip attached to a 1/32 in. (0.8 mm)

thick aluminum angle frame was installed along the edges of the calorimeter

box to provide an air-tight seal between the open face of the calorimeter

and the wall surface under test. The calorimeter had a metering area of 46

in. (1.17 m) by 75 in. (1.91 m), and was designed to accommodate test

structures with heat loss rates ranging from 0.3 to 19 Btu/h-ft 2 (0.9 to 60

W/m2

).

The portable calorimeter contained a 140 W electric resistance heater,

which consisted of a bare B. & S. (Brown and Sharpe) gauge No. 27 nickel

chromium wire with an electric resistance of 3.35 ohms per ft. (10.98 ohms

per meter). The heating wire was secured through steel springs and hooks

to ceramic stand-off insulators which were fastened to the plywood frame.

The wire spacing was varied to provide more heat in the bottom portion of

the calorimeter than the upper part. This was done to minimize the

vertical temperature gradient produced by the buoyancy effect within the

air space.

By maintaining no temperature difference between the interior and exterior

wall surfaces of the calorimeter, the amount of heat loss through the

calorimeter walls to the guarded room could be reduced. The temperature

differentials across the back wall of the calorimeter were monitored by an eighteen-junction pair thermopile with the thermocouple junctions placed on both the inner and outer faces of the wall. There were no thermocouple

junctions positioned on the side walls since the surface area of the sides

constituted only about 12% of total surface area of the calorimeter. The

thermocouples were constructed from B. & S. gauge No. 28 copper and

constantan wires with 0.0126 in. (0.32 mm) diameter and solid nylon

insulation. Figure 8.1 shows the construction details of the portable

calorimeter.

Using the thermopile output as the feedback variable, a voltage controller

was used to automatically control the operation of the electric heater and

maintain a zero temperature differential across the back calorimeter wall.

A safety thermostat with a sensing element installed inside the calorimeter

was connected to the heater to provide control of air temperature within

safe limits by opening the circuit at high temperature. The total electric

energy consumption of the heater was measured by a watt-hour meter

furnished with an optoelectronic device installed in the circuit. The

device consisting of a light-emitting diode and a detector. An electric

pulse was generated by the device each time 1.8 watt-hour of electricity

was consumed. The pulses were totaled by an electronic counter. Figure

8.2 shows the wiring schematic of the measurement /cont ro 1 system for the

'.alorimeter

.

The temperature of the exterior and interior air in the vicinity of heat

flow meters, and the air inside the calorimeter, were measured with

thermistors. These temperature sensors were a thermistor-resistor network

type and consisted primarily of a bead shaped thermistor and an external

network with a fixed precision resistor. The sensor possessed a resistance-temperature function which was very nearly linear over a specific temperature range. With an applied voltage of 1.2 volte to the

electric circuit, the thermistor produced an output voltage that was linear

with temperatures over a temperature range between -22 to 122°F (-30 to

111
50°C). Based on the data furnished by the manufacturer, measurement error

for the thermistors used is within +_ 0.5°F (0.3°C). The sensing element of

each thermistor was installed at a distance of 6 in. (152 mm) for the

exposed measurement surface. A micro-computer based data acquisition

system was used to monitor the output signals from the heat flow meters,

the portable calorimeter and the associated counter, and the thermistors.

The channels of all transducers were scanned every 2 seconds. For each

hour, the readings from each channel were averaged by the computer. At the

end of each one hour interval, the computer recorded the hourly averages on

a floppy disk for later analysis.

8.3 Test Results

The field measurements were performed in unoccupied rooms of selected floor

levels of office buildings situated in Ann Arbor, HI, Columbia, SC,

Springfield, MA, Huron, SD, Norfolk, VA, Pittsfield, MA and Anchorage, AK.

Construction details of the exterior walls and major building components on which heat flow measurements were carried out are summarized in table 8.1

The time variations of indoor and outdoor air temperatures and air-to-air

temperature difference across the external wall at the locations of a heat

flowmeter and the portable calorimeter for 3 daily cycles in the Huron

building are plotted in the upper portion of figure 8.3. The heat flow

meters were placed in the proximity of the calorimeter. At the bottom of

this figure, the corresponding measured rates of heat flow through the

metering area of the calorimeter and the wall area covered by the heat flow

meter are depicted as a function of time. As shown, the outdoor

temperature oscillated periodically around a mean level during a 24-hour

time interval. However, the indoor temperature was found to be relatively

constant. The surface heat flux changed in a periodic manner and lagged

behind the temperature difference between the indoor and outdoor air. This

thermal time lag was attributed to the heat storage in the wall and found

to be approximately 6 hours from visual inspection of the curves. This

time lag is the time required for the maximum heat flow to be reached after

the maximum temperature difference across the wall was attained.

During the measurements, the average temperature of the air inside the

calorimeter was about 2°F (1.1°C) lower than the indoor air temperature.

The heat flow rates measured by the calorimeter exhibit a similar periodic

variation as those determined by the heat flowmeter. However, the heat

flux values determined from data obtained by the calorimeter were

approximately 30% greater than those by the heat flow meter. The

calorimeter measurement included heat flow through the wall area containing

both highly conductive metallic framing members and the insulation filled

cavities between the framing, while the heat flow meter involved only heat

transmission through the area between the framing members.

The time variations of the daily and cumulative thermal resistances of wall

sections and major building components contained in the exterior wall of

the Huron building during a fifteen day measurement period are shown in

Figures 8.4 and 8.5. The thermal resistance R-value is defined as the

ratio of the average air-to-air temperature difference across a section of

the exterior wall to the average heat flow rate and is calculated from the

relation:

112
>T/q = f(AT) dt /

/*

Q

J o •/ o dt ( 8 . 1 )

where AT is interior-to-exterior air temperature difference, q is the heat

flow rate, and x is the measurement period or the period of integration.

Data were averaged over a 24-hour period in order to reduce the influence

of the transient effects of the exterior wall associated with its large

thermal inertia. The wall resistance values derived from the heat flow

meter, as shown in Figure 8.4, were the average values of the data from

eight heat flow meters placed on the interior wall surface below the

suspended ceiling. As can be seen in the figure, the R-values measured

with heat flow meter and the calorimeter varied over a 24-hour period.

These changes were due to daily variations in the outdoor temperature as illustrated in the upper part of Figure 8.4, and the ambient airflow, which

affected the thermal resistance of the air film at the outer surface of the

exterior wall.

The cumulative averages of daily thermal resistance values for the wall,

the upper wall located in the ceiling plenum, and structural beam and

column are calculated by dividing the sum of the daily average thermal

resistance by the elapsed days, and are plotted in Figures 8.4 and 8.5 for

comparison. Based on the fifteen days of measurements using heat flow

meters, the measured overall thermal resistances at the wall, the upper

wall, and structural beam and column were found to be 20.4, 21.0, 10.4, and

9.5 ft -h-°F/Btu (3.6, 3,7, 1.8, and 1.7 m -K/W) respectively. As shown in

Figures 8.4 and 8.5, the cumulative average resistance values were

generally within 5% of its final value after 2 days of measurements. The

low thermal resistance of the structural beam and column shown in Figure

8.5 were attributed to highly conductive heat flow paths or thermal bridges

contained in these sections of the building envelope.

The average wall resistance values as measured by heat flow meters, and by

the portable calorimeter, are plotted in Figure 8.6 as a function of

measurement period for the Huron building. Also plotted in the figure are the corresponding values of the standard deviation.

As stated earlier, the large thermal mass of the external wall, which was subject to a varying air temperature at the outer surface, caused the heat

flow to lag behind the temperature difference driving force. A prolonged

measurement period is required for the results of wall thermal resistance

calculations to converge to a constant value. As shown in Figure 8.6, both

the variation in the wall thermal resistances and its associated standard

deviation generally decrease with an increase in the length of the

measurement period. Thermal resistance values calculated from data

obtained by the calorimeter were approximately 30% lower than values

obtained with heat flow meters. As mentioned previously, this difference

was attributable to the effect of wall framing members.

In Table 8.2, a comparison is made of the thermal resistance values, as measured using heat flow meters and the portable calorimeter, and the

corresponding predicted steady-state values. Also presented in the table

are heat flow rates, and the outdoor and indoor air temperatures. All the

data tabulated in table 8.2 are averages obtained on 2 to 16 consecutive

24-hour cycles. The predicted steady-state thermal resistance values were

113
calculated using the series resistance method [8] and the published data

include manufacturer's literature on thermal properties of the building

materials involved. The thermal resistances of air films at the interior

and exterior surfaces used in the calculations were 0.68 ft^-h°F/Btu (0.12

m -K/W) and 0.17 ft -h-°F/Btu (0.03 m^-k/W), respectively.

Inspection of table 8.2 shows that a fairly good correlation exists between

the measured R-values and the predicted results. The significant

disagreement between the measured and calculated results for the structural

column in the Anchorage building may be due to the fact that the resistance

calculations did not reflect multi-dimensional heat flow conditions. In

general, the portable calorimeter gave lower wall resistance values than

the heat flow meters. For these tests, the wall framing members and

fasteners reduced the overall resistances by approximately 33% compared to

the same walls without taking the framing effects into account. The

significantly high wall resistance determined by the portable calorimeter

for the Columbia building was probably attributable to the additional heat

conducted laterally into the measured area from a nearby hot air duct.

The thermal resistance values of various building components measured with

heat flow meters are plotted in figure 8.7 against the corresponding

predicted steady-state values. It appears from this plot that the linear

correlation between these two variables is fairly good because all the

points fall around the line of best fit obtained from the least squares

method. The standard error of estimate and the coefficient of correlation,

which is a measure of the degree of linear association between the measured

and predicted thermal resistance values, were found to be 3.61 ft^-h°F/Btu

(0.64 m -K/w) and 0.87, respectively. Some significant variations in

resistance values were attributable to differences in construction

workmanship, assembly techniques, defective insulation, aging building

materials, difference between the actual material thermal properties and

the handbook values, and the presence of moisture.

8.4 Conclusions

Reliable thermal resistance values of building envelopes can be derived

from in situ measurements of indoor-outdoor air temperature differences and

of heat flow across test structures provided that the measurements are

carried out over a sufficiently long period. A measurement period of at

least two days is recommended, but an entire week of data collection is

advisable when possible. Both the heat flow meters and the portable

calorimeter were found to be useful tools for measuring heat flow through

large, non-homogeneous building assemblies in the field. Wall thermal

resistances derived from data obtained using a portable calorimeter yield

lower values than those obtained with heat flow meters. This difference is

attributed to the additional heat flow through highly conductive framing

members in the structure. The thermal resistance values of masonry

exterior walls of seven office buildings situated in various climate zones have been found to vary widely from approximately 8 to 39 ft^-h-°F/Btu (2

to 7 m^-K/W). The measured thermal resistances deviated from the design

thermal resistances by an average of 14%, the worst case being 45%.

114
Table 8.1

Construction Details of Building Components in Test Buildings

A. The Ann Arbor building

1.

Wall located below the suspended ceiling:

0.5 in (13 mm) Quarry tile, 1 in (25 mm) metal lath and mortar

bed, 10 in (254 mm) concrete masonry unit, 1.5 in (38 mm)

semirigid glass fiber insulation board, and 0.63 in (16 mm)

acoustic wall panel.

B. The Columbia building

1. Wall below the acoustic tile ceiling:

12 in (305 mm) precast concrete panel, 2 in (51 mm) glass fiber

blanket insulation, 0.63 in (16 mm) gypsum wallboard on 2 in (51

mm) metal studs.

2. Wall above acoustic tile ceiling:

8 in (203 mm) precast concrete panel, 24 in (610 mm) air space

inside concrete overhang, 3 in (76 mm) precast concrete panel, 2

in (51 mm) glass fiber blanket insulation, and 0.63 in (16 mm)

gypsum wallboard on 2 in (51 mm) metal studs.

3. Concrete wall inside the ceiling plenum:

15 in (381 mm) precast concrete panel.

C. The Springfield building

1. Walls located below and above acoustical tile ceiling:

5.5 in (140 mm) precast concrete panel, 2.5 in (64 mm) semirigid

glass fiber insulation board, and 0.5 in (13 mm) gypsum

wallboard

.

2. Structural column:

5.5 in (140 mm) precast concrete panel, 2.5 in (64 mm) semirigid

glass fiber insulation board, fire-proof steel beam, and 0.5 in

(13 mm) gypsum wallboard on 2.5 in (64 mm) metal studs as the

column enclosure.

D. The Huron building

1. Wall below acoustical tile ceiling:

4 in (102 mm) face brick, 6 in (152 mm) light weight concrete

masonry unit, 3 in (76 mm) semirigid glass fiber insulation

board, and 0.63 in (16 mm) gypsum wallboard.

2. Wall inside the ceiling plenum:

Same as above.

115
Table 8.1 (continued)

E. The Norfolk building

1. Wall below acoustical tile ceiling:

4 in (102 mm) face brick, 0.75 in (19 mm) air space, 0.5 in (13

mm) gypsum board sheathing, 4 in (102 mm) glass fiber blanket

insulation, and 0.5 in (13 mm) gypsum wallboard.

2. Structural column:

4 in (102 mm) face brick, 0.75 in (19 mm) air space, 0.5 in (13

mm) gypsum board sheathing, 4 in (102 mm) glass fiber blanket

insulation, structural column with spray-on fire proofing, and

0.5 in (13 mm) gypsum board enclosure.

3. Structural beam inside the ceiling plenum:

4 in (102 mm) face brick. 0.75 in (19 mm) air space, 0.5 in (13

mm) gypsum wallboard, and structural beam with spray-on fire

proofing.

F. The Pittsfield building

1. Wall below the suspended ceiling:

4 in (102 mm) face brick, 2 in (51 mm) semirigid glass fiber

insulation board, 6 in (152 mm) solid masonry concrete block, and

4 in (102 mm) face brick.

2. Wall inside the ceiling plenum:

4 in (102 mm) face brick, 2 in (51 mm) semirigid glass fiber

insulation board, 4 in (102 mm) face brick, 10 in (254 mm)

airspace, and 4 in (102 mm) masonry concrete block.

3o Structural column:

4 in (102 mm) face brick, 0.5 in (13 mm) thick pre-molded

expansion filler, 10 x 7 in (254 x 178 mm) steel column, and 1 in

(25 mm) particle board with plastic laminated face.

G. The Anchorage building

1. Wall below the suspended ceiling:

5 in (127 mm) precast concrete panel, 3 in (76 mm) semirigid

glass fiber insulation board, 4 in (102 mm) glass fiber batt

insulation, and 0.63 in (16 mm) foil backed gypsum wa 1 lboard on

metal studs.

2. Wall inside the ceiling plenum:

5 in (127 mm) precast concrete panel, and 3 in (76 mm) semirigid

glass fiber insulation board with spray-on fireproofing.

3 . Roof deck inside the ceiling plenum:

1 in (25 mm) concrete paver, 3 in (76 mm) semirigid glass fiber

insulation board, and 6 in (152 mm) lightweight aggregate

concrete roof slab on corrugated steel deck tied to wall

structure

.

116
Table 8.1 (continued)

4. Mirror wall:

0.25 in (6 mm) reflective tempered glass, 4 in

fiber batt insulation, and 0.63 in (16 mm) foil

wallboard on metal studs.

(102 mm) glass

backed gypsum

117
Table 8.2

Comparison of Wall Thermal Resistances Measured

with a Portable Calorimeter (PC) and Heat Flow

Meters (HFM) to Corresponding Design Values

Air Temp Heat Flow R-Value, ft 2-h-°F/Btu

Building

Building

Component

°F

Hot

Side

(°c)

Cold

Side

Rate

Btu/h-ft 2

(W/m2

)

(m2 -K/W)

Measured Predicted

PC HFM Value

Ann Arbor

,

1. Wall 68.1 39.4 2.49 11.1 11.5 10.6

MI (20.1) (4.1) (7.85) (1.95) (2.03)

2. Structural 65.1 39.4 5.85 4.40 3.7

Beam (18.4) (4.1) (18.4) (0.77) (0.66)

3. Structural 68.9 39.4 2.22 13.3 8.8

Column (20.5) (4.1) (7.00) (2.34) (1.55)

Columbia, 1. Wall 70.3 47.9 2.08 15.1 10.8 11.2

SC (21.3) (8.8) (6.56) (2.66) (1.89) (1.97)

2. Upper 69.1 47.9 2.76 7.7 9.4

Wall (20.6) (8.8) (8.70) (1.35) (1.66)

3. Concrete 69.1 47.9 4.75 4.5 3.9

Wall (20.6) (8.8) (15.0) (0.79) (0.68)

4. Concrete 69.1 47.9 3.64 5.8 4.5

Beam (20.6) (8.8) (11.5) (1.03) (0.78)

Springfield

,

1. Wall 69.5 41.9 2.20 6.8 12.6 13.0

MA (20.8) (5.5) (6.92) (1.20) (2.21) (2.29)

2. Upper 69.9 41.9 2.50 11.2 13.0

Wall (21.1) (5.5) (7.88) (1.97) (2.29)

3. Structural 69.3 41.9 2.33 11.8 13.0

Column (20.7) (5.5) (7.35) (2.07) (2.29)

Huron

,

1. Wall 66.9 37.9 1.42 12.0 20.4 16.9

SD (19.4) (3.3) (4.48) (2.11) (3.59) (2.97)

2. Upper 63.8 37.9 1.23 21.0 16.9

Wall (17.7) (3.3) (3.88) (3.70) (2.97)

3. Structural 63.8 37.9 2.49 10.4 15.6

Beam (17.7) (3.3) (7.85) (1.83) (2.75)

4. Structural 66.6 37.9 3.02 9.5 9.7

Column (19.2) (3.3) (9.52) (1.67) (1.71)

118
Table 8.2 (continued)

Building

Building

Component

Air Temp

°F (°C)

Hot Cold

Side Side

Heat Flow

Rate

Btu/h-f

t

2

(Vim2

)

R-Value , ft 2-h-°F/Btu

(m2 -K/W)

Measured Predicted

PC HFM Value

Norfolk

,

1. Wall 77.2 48.4 3.36 8.6 15.7

VA (25.1) (9.1) (10.6) (1.51) (2.76)

2. Structural 77.7 48.4 1.98 14.8 15.7

Column (25.4) (9.1) (6.24) (2.61) (2.76)

3. Structural 78.4 48.4 1.11 27.2 22.1

Beam (25.8) (9.1) (3.48) (4.78) (3.88)

Pittsfield

,

1. Wall 77.8 38.7 3.81 10.3 11.8

MA (25.4) (3.7) (12.0) (1.81) (2.07)

2. Upper 78.0 38.7 4.02 9.8 4.6

Wall (25.6) (3.7) (12.7) (1.72) (1.93

3. Structural 77.5 38.7 6.62 5.9 4.6

Column (25.3) (3.7) (20.9) (1.03) (0.81)

Anchorage

,

1. Wall 73.2 50.6 0.70 32.0 29.9

AK (22.9) (10.3) (2.21) (5.64) (5.27)

2. Upper 69.2 50.6 0.85 21.7 14.6

Wall (20.7) (10.3) (2.71) (3.81) (2.56)

3. Structural 69.2 50.6 1.59 11.7 15.1

Column (20.7) (10.3) (5.01) (2.06) (2.66)

4. Roof Deck-Webs

Lower 69.6 50.6 1.07 17.8 20.4

(20.9) (10.3) (3.37) (3.13) (3.59)

Upper 69.6 50.6 0.64 29.6

(20.9) (10.3) (2.02) (5.21)

5. Mirror 73.8 50.6 0.87 26.7 17.1

Wall (23.2) (10.3) (2.74) (4.70) (3.01)

119
8"

(203mm)

Figure 8.1 Construction Details of Portable

Calorimeter

120
Figure 8.2 Schematic of the Measurement/Control

System of the Portable Calorimeter

121
20

15

E 10

UJ

GCD

5

5

ffi CL§ 0

cr< -5

-10

60 -

10 -

TEMP. TEMP. DIFF.

• Indoor • Heat flux transducer

t Outdoor o Calorimeter

60

35

30 E

111 O

25 |

HILL

y_ 20 5

UJ

GC3

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15 < ° GCUJ

0.5

io y

“10 _

CME

X

D

-I

U.I—<

HII

UJo

<

Li- CC3

co

TIME (h)

Figure 8.3 Indoor and Outdoor Temperatures, Temperature Difference

Across Wall and Surface Heat Fluxes Measured with Heat

Flux Transducers and the Calorimeter

122
10

o

LU

crz>K

<

crLU

QLU

-5

cr<

-10

-15 -

30

LUO

20 5

cr

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cr

cr

LUX

H 1 -

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£

TIME (day)

Figure 8.4 Long Term Variations in Heat Flux Transducer

and Calorimeter Measurements of a Wall Section

123
Figure 8.5 Long Term Variations of Thermal Resistance Measurement

of the Upper Wall and Structural Beam and Column

124

(m

2

-KW)
WALL

THERMAL

RESISTANCE

(m

2

-K/W)

Figure 8.6 Effects of Measurement Period on Average Wall R-Values

Determined by Heat Flux Transducer and Calorimeter

125

STANDARD

DEVIATION

(m

2

-K/W)
(m2-K/W)

5 10 15 20 25

PREDICTED R-VALUE (ft2-h-°F/Btu)

Figure 8.7 Comparison between the Measured Thermal Resistance

and the Predicted Steady-State Resistance Values

126

(m

2

-K/W)
9.0 Heat Losses Due to Thermal Bridges

9.1 Introduction

The thermographic inspection of the federal buildings revealed that four of

the buildings have a number of highly conductive heat flow paths, referred

to as thermal bridges, which conduct excessive heat around the insulation

and cause abnormal escape of heat from the building. In better insulated

buildings the heat losses associated with thermal bridges are more

pronounced [28]

.

In general, a thermal bridge has a smaller cross-sectional area and

contains material with less thermal resistance than the adjacent areas of

the building envelope. During the heating season, the thermal bridge

results in a rise in the external and a decrease in the internal surface

temperature in the region of the building envelope where the thermal bridge

occurs. The thermal bridge also causes a higher rate of outward heat flow

relative to adjacent areas. During the cooling season, the process is

reversed, resulting in increased heat gains. At external wall-floor

interfaces, where concrete walls with layers of interior insulation are

penetrated by concrete deck floors or internal walls, the thermal bridges

may increase the envelope heat loss by 50% [30], Condensation of moisture

at interior surfaces can occur at the location of thermal bridges and cause

rapid deterioration of building materials.

9.2 Description of the Thermal Bridges Found in the Building Envelopes

An example of structural thermal bridges found in the north wall of the

office building located in Huron, SD is illustrated in the thermogram shown

in figure 9.1. This thermogram was obtained from ground based

thermographic inspections of the building envelope. The bright horizontal

lines shown in the figure are thermal bridges at the exterior

wal 1/ intermediate floor intersection. The bright region in the right of

figure 9.1 does not constitute a thermal bridge but rather is caused by the

glass windows located near an entrance to the building.

Figure 9.2 shows a thermogram of the stone faced wall of the building

located in Ann Arbor, MI. The horizontal and vertical bright lines in the

picture indicate thermal bridges caused by the penetration of intermediate

concrete slab floors and structural columns in the exterior wall. A

thermogram showing the upper portions of the external walls of the building

in Anchorage, AK is given in Fig 9.3. The horizontal and vertical bright

stripes in this thermogram depict thermal bridges resulting from the

penetration of concrete floors and structural columns through an insulated

exterior wall.

Figure 9.4 shows thermal anomalies observed in a precast concrete panel of an exterior wall of the building in Columbia, SC. The long horizontal and

vertical luminous lines show the thermal bridges caused by high heat

conduction through the window overhangs and decorative columns that

penetrated the insulated wall.

Construction details of the portions of the building envelope where the

thermal bridges occurred in the buildings studied are shown in figures 9.6

through 9.8. The specification of the materials used in each wall section

127
is given in the table 9.1. As can be seen from figures 9.5 through 9.8,

the insulation layers in these composite walls are penetrated by the

concrete floor assemblies. The thermal conductivity and diffusivity of

concrete are about 20 and 3 times greater, respectively, than those of

glass fiber insulation. Significant heat flow through these paths during

the heating and cooling seasons can be anticipated.

9.3 Instrumentation and Procedures

The equipment used to measure the rate of heat transfer through the

building envelopes included heat flux tranducers and temperature sensors that were interfaced to a microcomputer. Each heat flux transducer

consisted of a 4-inch (102 mm) diameter thin, flat circular disk with an embedded thermopile. The hot and cold junctions of the thermopile were

located on opposite faces of the disk to measure the temperature gradiants

and therefore the beat flow through it. The measurement system could

simultaneously measure up to 13 temperatures and 15 heat fluxes. The

computer continuously scanned all sensors, computed time-averaged values

every 2 seconds. From these values average hourly values were computed and

stored on a floppy disk for subsequent processing. Upon completion of the

field tests, the heat flux transducers were calibrated using a guarded hot

plate apparatus described in references 26 and 27. During the calibration

the transducers were subjected to a range of uniform heat fluxes at the

mean temperatures corresponding to those experienced during the field

tests. The accuracy of the heat transducers calibration was estimated to

be within +_ 1%.

To perform field measurements, four to eight heat flux transducers were

attached by masking tape to selected locations on the interior wall

surfaces, one each on the structural beam and column, and four transducers

on the roof assembly of the test building. The measurement stations were chosen based on the locations of thermal bridges found in the exterior

thermograms of the buildings involved. During installation a stud finder

was used to make certain that the transducers were not installed over

metallic wall framing members.

Thermistors were used to measure the temperature of the air outside the

building and the indoor air in close proximity of heat flux transducers.

The sensing element of the thermistor was placed 6 in. (152 mm) from the

exposed surface where surface heat flux was determined.

9.4 Test Results

The results of field measurements taken over a period of 2 to 16 days

between February and May of 1983 are summarized in table 9.2. The air

temperature and heat flow rate values shown in table 9.2 represent the mean values of daily average air temperatures and surface heat fluxes. Test

periods consisting of multiples of 24-hours were chosen to minimize the

transient effects on heat flow measurements and thermal resistance

calculations associated with thermal storage within building components.

The thermal resistance values shown in table 9.2 represent average Rvalues, defined as the ratio of the average air-to-air temperature

difference across the building envelope component to the average heat flow

rate over the test period. Also presented are the corresponding predicted

128
steady-state thermal resistance values. Predicted resistance values were

calculated from published data on the thermal properties of the building

materials used, employing the series resistance method [8]. In performing

these calculations the thermal resistances of air films was assumed to be

0.68 ft -h-°F (0.12 m^-K/W) on the inside surface and 0.17 ft^-h-°F (0.03

m -K/W) on the outside surface. These values are considered to be typical

of interior and exterior vertical surfaces where the room is at normal

temperature and when the exterior surface is exposed to a 15 mph (6.7 m/s)

wind

.

Table 9.2 shows that the measured and predicted R-values are in general

agreement except for the structural column in the Anchorage building. The

discrepancy observed in the Anchorage building is attributed to the fact

that the simple parallel heat flow method used in performing the thermal

resistance calculations is probably not applicable to the cases of the

complex structural column and roof deck assembly.

Estimates of the contributions of thermal bridges to the heat losses in the

office buildings measured are summarized in table 9.3. These data were

derived from heat flux data obtained at the thermal bridges and

computations (from an examination of the thermograms and architectural

drawings) of the surface areas occupied by the thermal bridges. As can be seen in table 9.3 the thermal bridges resulted in a 62 to 118% increase in

the rate of heat flow relative to the wall locations free from thermal

bridges. The total cross-sectional area of the thermal bridges was

estimated to occupy from 9 to 18% of the wall area depending upon the

building. The overall effect of thermal bridges was to increase wall heat

transmission from 10 to 21%.

The data presented in table 9.2 are for steady state conditions. However,

the response of a thermal bridge is dynamic. Diurnal variations in the

outdoor and indoor air temperatures and heat fluxes measured at each site

are presented in figures 9.9 through 9.12. Also plotted in the figures are the temperature differences across the walls, and between the outdoor air

and the air in the proximity of the structural beam and the roof deck

inside the ceiling plenum.

Inspection of figures 9.9 to 9.12 shows that the temperature of the outdoor

air varied periodically over 24 hours, with the minimum temperature

occurring in the early morning and the peaks in the early afternoon.

However, the indoor air temperatures were found to be stable throughout the

24-hour period. The rates of heat flow through the interior surfaces of

various components were also found to fluctuate with time. Moreover, the

temperature and heat flow data were about 90 degrees out of phase.

Specifically, the maximum or minimum heat fluxes shown at the bottom of

figures 9.9 to 9.12, were consistently lagging behind the

temperature driving force by approximately 5.5, 7.5, 5.4 and 7.2 hours for

the Huron, Ann Arbor, Anchorage, and Columbia buildings, respectively.

These time differences were attributed to thermal storage.

9.5 Mathematical Modeling

In order to predict the amount of heat loss due to thermal bridges, a computer program called HEATING6 developed by Oak Ridge National Laboratory

[31] was used to analyze the thermal fields around the exterior

129
wa 1 1/ intermediate floor systems. This computer model uses a finitedifference method to solve multi-dimensional, steady-state and transient

heat conduction problems associated with various types of complex

structures

.

A two dimensional heat flow model containing 1,059 nodes was developed. It

simulates transient heat conduction within the multi-layered wall/floor

system corresponding to the construction details at the Huron building (see

figure 9.5). In executing the code it was assumed that the structure was

exposed on one side to a time varying sinusoidal temperature, while on the

other side the temperature remained constant throughout.

Figure 9.14 shows the predicted heat fluxes for the interior wall surface,

the top of the slab floor, and the exposed surface of the lower inner wall

containing the structural beam. These data were obtained by summing the

contributions from the steady state condition with a temperature difference

across the wall of 30.5°F (16.9°C), and a 24-hour periodic component having

an amplitude of +. 12°F (6.7°C). These values were used because they

corresponded to the changes observed in the outdoor air temperature on two

consecutive days (see figure 9.9). A convective heat transfer coefficient

of 1.47 Btu/h-f t-°F (8.35 W / m^-K) was assumed for both the interior and

exterior surfaces. The zero on the abscissa of figure 9.14 represents the

intersection of the vertical interior wall surface and the top surface of

the horizontal slab floor. Values below zero correspond to points along

the top surface of the floor, or the lower wall containing the beam. Heat

fluxes corresponding to heat flowing from inside to outside the building

were assigned positive values. Added to figure 9.14 are the ranges of

surface heat fluxes measured on April 7 on the interior wall surface at the

mid-height of the structural beam at the Huron building. The agreement

between the measured values and the predicted values is good as can be seen in figure 9.14.

It should be noted that the model predicts significantly higher heat fluxes

at points such as the wall/floor corner and the concrete floor where

measurements could not be made. An integration of the predicted heat

fluxes over the area of the thermal bridge increases the contribution of

the thermal bridge to the total wall heat loss by approximately a factor of

two. However, additional experimental work is required to ascertain the

heat fluxes along points on the thermal bridge where measurements could not

be performed.

Figure 9.15 depicts the predicted heat flux on the exterior wall surface

for several times throughout the day, plotted as a function of position.

These values were calculated for an average air-to-air temperature across the wall of 40°F (22°C) and for an amplitude of +. 15°F (8.3°C). As the

temperature level of the air adjacent to the exterior wall surface changed

sinusoidally, the transient effect caused varying amount of heat to flow

periodically in or out from the exterior wall. Moreover, as shown in

figure 9.5, in the regions around the thermal bridges more heat was

dissipated than in the adjoining areas.

9.6 Conclusions

The inspection of the exterior envelope of four federal office buildings

using infrared thermography revealed the existence of thermal bridges. The

130
measurement of the heat flow through these thermal bridges using heat flow

meters showed that the heat flux at the thermal bridges were from 62 to

118% greater than the heat flux on the insulated sections of the walls.

Examination of thermograms obtained at each building and architectural

drawings showed that the thermal bridges represented from 9 to 18% of the

buildings insulated wall areas. Therefore, the thermal bridges increased

the wall heat loss by approximately 10 to 21% relative to the same wall

structures without thermal bridges. A two-dimensional finite difference

heat flow model was used to simulate the transient response of the thermal

bridge representing an exterior wal 1/ intermediate floor system. At points

at which heat flow measurements could be made, the model predicted the

measured heat flux well. Moreover, the model predicted even higher heat

fluxes at other points on the thermal bridge where measurements could not

be made. Therefore, the total contribution of thermal bridges to heat loss

is probably even greater, perhaps by a factor of two, than that cited

above. Additional experimental work is needed to confirm this possibility.

131
Table 9.1

Details of Building Components in Thermal Bridge Measurements

A. The Huron building

1. Wall located below acoustical tile ceiling:

4 in. (102 mm) face brick, 6 in. (152 mm) light-weight concrete

masonry unit, 3 in. (76 mm) semirigid glass fiber insulation

board, and 0.63 in. (16 mm) gypsum wallboard.

2. Wall inside the ceiling plenum:

Same as above.

3. Structural beam in the ceiling plenum:

4 in. (102 mm) face brick, 4 in. (102 mm) light-weight concrete

masonry unit, 3 in. (76 mm) semirigid glass fiber insulation, and

W24x84 steel beam with a 2 in. (51 mm) minimum fire proofing.

4. Structural column:

4 in. (102 mm) face brick, 4 in. (102 mm) concrete masonry unit,

structural column with 2 in. (51 mm) spray-on fire proofing, and

0.63 in. (16 mm) gypsum wallboard on metal studs as column

enclosure.

B. The Ann Arbor building

1. Wall below the suspended ceiling:

0.5 in. (13 mm) Quarry tile, 1 in. (25 mm) metal lath and motor

bed, 10 in. (254 mm) concrete masonry unit, 1.5 in. (38 mm)

semirigid glass fiber insulation board, and 0.63 in. (16 mm)

acoustic wall panel.

2. Beam section inside the ceiling plenum:

0.5 in. (13 mm) Quarry tile, 1 in. (25 mm) metal lath and motor

bed, 4 in. (102 mm) concrete masonry unit, and W21x44 steel beam

with spray-on fire proofing.

O 3. Structural column:

0.5 in. (13 mm) Quarry tile, 1 in. (25 mm) metal lath and motor

bed, 10 in. (254 mm) concrete masonry unit, 1.5 in. (38 mm) glass

fiber blanket insulation, structural column with spray-on fire

proofing, and 0.63 in. (16 mm) plaster on 0.63 in. (16 mm) gypsum

lath on 3.3 in. (84 mm) metal studs.

C. The Anchorage building

1. Wall below the suspended ceiling:

5 in. (127 mm) precast concrete panel, 3 in. (76 mm) semirigid

glass fiber insulation board, 4 in. (102 mm) glass fiber batt

insulation, and 0.63 in. (16 mm) foil backed gypsum wallboard on metal studs.

132
2. Wall inside the ceiling plenum:

5 in. (127 mm) precast concrete panel, 3 in. (76 mm) semirigid

glass fiber insulation board with spray-on fire proofing.

3. Roof deck in the ceiling plenum:

1 in. (25 mm) concrete paver, 3 in. (76 mm) semirigid glass fiber

insulation board, and 6 in. (152 mm) light weight aggregate

concrete roof slab on corrugated steel deck connecting to wall

structure

.

4. Structural column:

5 in. (127 mm) precast concrete panel, 3 in. (76 mm) semirigid

glass fiber insulation board, 20 x 20 in, (508 x 508 mm) steel

column with spray-on fire proofing, and 0.63 in. (16 mm) gypsum

board as column enclosure.

D. The Columbia building

1. Wall below acoustic tile ceiling:

12 in. (305 mm) precast concrete panel, 2 in. (51 mm) glass fiber

blanket insulation, and 0.63 in. (16 mm) gypsum wa 1 lboard on 2 in. (51 mm) metal studs.

2. Wall above acoustic tile ceiling:

8 in. (203 mm) precast concrete panel, 24 in. (610 mm) air space

inside concrete overhang, 3 in. (76 ram) precast concrete panel, 2 in. (51 mm) glass fiber blanket insulation, and 0.63 in. (16 mm)

gypsum wallboard on 2 in. (51 mm) metal studs.

3. Concrete wall inside the ceiling plenum:

15 in. (381 mm) precast concrete panel.

4. Concrete beam inside the ceiling plenum:

10 in. (254 mm) precast concrete panel, and 18 in. (457 mm)

reinforced concrete beam.

133
Table 9.2

Measured Heat Flow Rates and Thermal Resistance Values

Building Components in Thermal Bridge Analysis

Daily Daily

Bui Id in

e

Component

Average

Air Temp

°F (°F)

Hot Cold

Side Side

Average

Heat Flow

Rate

Btu/h-ft^

(W/m2

)

Thermal

ft*-1

(m

Measured

Value

Huron

,

SD

1. Wall 66.9

(19.4)

37.9

(3.3)

1.42

(4.48)

20.4

(3.59)

2. Upper

Wall

63.8

(17.7)

37.9

(3.3)

1.23

(3.88)

21.0

(3.70)

3. Structural 63.8

(17.7)

37.9

(3.3)

2.49

(7.85)

10.4

(1.83)

4. Structural

Column

66.6

(19.2)

37.9

(3.3)

3.02

(9.52)

9.5

(1.67)

Ann Arbor,

MI

1. Wall 68.1

(20.1)

39.4

(4.1)

2.49

(7.85)

11.5

(2.03)

2. Structural 65.1

(18.4)

39.4

(4.1)

5.85

(18.44)

4.4

(0.77)

3. Structural 68.9

(20.5)

39.4

(4.1)

2.22

(7.00)

13.3

(2.34)

Anchorage

,

AK

1. Wall 73.2

(22.9)

50.6

(10.3)

0.70

(2.21)

32.0

(5.64)

2. Upper

Wall

69.2

(20.7)

50.6

(10.3)

0.86

(2.71)

21.7

(3.81)

3. Roof DeckWebs

Lower 69.6

(20.9)

50.6

(10.3)

1.07

(3.37)

17.8

(3.13)

Upper 69.6

(20.9)

50.6

(10.3)

0.64

(2.02)

29.6

(5.21)

4. Structural

Column

69.2

(20.7)

50.6

(10.3)

1.59

(5.01)

11.7

(2.06)

of

Resistance

i-°F/Btu

: -K/W)

Predicted

Value

16.9

(2.97)

16.9

(2.97)

15.6

(2.75)

9.7

(1.71)

10.6

(1.87)

3.7

( 0 . 66 )

8.8

(1.55)

29.9

(5.27)

14.6

(2.56)

20.4

(3.59)

17.1

(3.01)

15.1

( 2 . 66 )

134
Bui lding

Columbia

,

SC

Daily

Average

Air Temp

°F (°F)

Hot Cold

Component Side Side

1. Wall 70.3 47.9

(21.3) (8.8)

2. Upper 69.1 47.9

Wall (20.6) (8.8)

3. Concrete 69.1 47.9

Wall (20.6) (8.8)

4. Concrete 69.1 47.9

Beam (20.6) (8.8)

Daily

Average

Heat Flow

Rate

Btu/h-f

t

2

(W/m2

)

Thermal Resistance

ft 2-h-°F/Btu

(m2-K/W)

Measured Predicted

Value Value

2.08 10.8 11.2

(6.56) (1.89) (1.97)

2.76 7.7 9.4

(8.70) (1.35) (1.66)

4.75 4.5 3.9

(15.0) (0.79) (0.68)

3.64 5.8 4.5

(11.5) (1.03) (0.78)

135
Table 9.3

Estimates of the Heat Losses Resulting

from Thermal Bridges

Office

Building

Increased Wall

Heat Flow Rate*

(%)

Percent of Wall

Occupied by Thermal

Bridge

Percent Increase in

Total Wall Heat Flow

Caused by

Thermal Bridge

Huron

,

South Dakota

108 9 10

Ann Arbor

,

Michigan

62 17 11

Anchorage

,

Alaska

118 18 21

Columbia,

South Carolina

74 16 12

*Note: The ratio of the heat flux difference between the walls with and

without thermal bridges to the surface heat flux at the wall with

no thermal bridges.

136
Figure 9.1 Thermal Bridges Found

in the Exterior Wall

of the Huron Office

Building

Figure 9./ iuccuuu

Occurring in the

Ann Arbor Building

Figures 9.3 Thermal Bridges Observed

in Upper Floors of the

Anchorage Building

Figure 9.4 Thermal Bridges

Occurring in the

Columbia Building

137
HEAT FLUX TRANSDUCER

3/4" (19mm)

EXPANSION

JOINT

4" (102mm)

FACE

BRICK

5/8" (16mm) GYPSUM BOARD

3" (76mm) SEMI-RIGID FIBER GLASS

INSULATION BOARD

6" (152mm) VERTICALLY REINFORCED

LIGHT WEIGHT CONCRETE BLOCK

(every 2nd block cores reinforced

vertically with fill cores)

4" (102mm) VINYL BASE

5- 1/4* (133mm) CONCRETE FLOOR

SLAB ON STEEL DECK

SPRAY-ON CEMENTITIOUS

MIXTURES (2" (51mm) minimum

fire proofing)

HEAT FLUX TRANSDUCER

4" (102mm) REINFORCED LIGHT WEIGHT

CONCRETE MASONRY UNIT

STEEL BEAM W24x84

5/8" (16mm) GYPSUM BOARD

Figure 9.5 Construction Details and Sensor Locations on the

Exterior Wall in the Huron Office Building

138
Figure 9.6 Construction Details of the Exterior Wall

in the Ann Arbor Office Building

139
5* (127mm)

PRECAST

CONCRETE

EXPANSION

JOINT

3" (76mm)

SEMI-RIGID

INSULATION

1" (25mm) INSULATING GLASS WINDOW

4" (102mm) BATT INSULATION

FIN RADIATION ASSEMBLY

5/8" (16mm) FOIL BACKED GYPSUM

BOARD

6" (152mm) CONCRETE FLOOR ON

STEEL DECK

STEEL BEAM

5/8" (16mm) GYPSUM BOARD

ON 2-1/2" (64mm) METAL

STUDS

FIRE PROOFING

Figure 9,7 Construction Details of the Exterior Wall

in the Anchorage Office Building

140
Carpet on 4"(102mm) access flooring

•. •• a

-

.

*' 1 ,P; if -

' f.V

7 •

. •*'

P/'.J

4"(102mm) concrete floor over

18"(457mm) reinforced concrete beam

Acoustical ceiling

5/8"(16mm) gypsum board on metal studs

Precast concrete panel

Vertically pivoted glass/aluminum frame

window

5/8"(16mm) gypsum board on 2"(51mm)

metal studs

2”(51mm) fiber glass blanket insulation

12"(305mm) precast concrete panel

4"(102mm) resident base

Figure 9.8 Construction Details of the Exterior Wall

in the Columbia Office Building

141
SURFACE

HEAT

FLUX

(Btu/h-ft

2)

TEMPERATURE

DIFFERENCE

<°F)

AIR

TEMPERATURE

<°F)

Figure 9.9 Temperature and Heat Flux in the Huron

Building as a Function of Time

SURFACE

HEAT

FLUX

(W/m 2)

TEMPERATURE

DIFFERENCE

(°C)

AIR

TEMPERATURE

(°C)
70

60

50

40

30

1 40

30

20

10 . 7

6

5

4

3

2

1

» Indoor Temperature

• Outdoor Temperature

19 13

I 19

° Temperature Diff. (indoor-outdoor)

• Temperature Diff. (ceiling plenum-outdoor)

19 ~

I

1 13 ~

1

19

l

1

* Column

* Beam

° Wall

x X X X X

I 19 1 2/16/83

13

2/17/83

TIME (h)

20

15

10

O

LU

oe<

DC

LLI Q.2

LU

L—

DC<

0

13

20

LU O

DC ~

= LU 15 s I

isLL 10

13

- 20

18 cnTE

16 5

22

- 14

12

10

H8

6

19 1 7 13

2/18/83

x

D

<

LUX

UJO

<

u_

DCCO

ire 9.10 Temperature and Heat Flux in the Ann

Arbor Building as a Function of Time

143
80

25

5 / 7/83 5/ 8/83

TIME (h)

Figure 9.11 Temperature and Heat Flux in the Anchorage

Building as a Function of Time

144

SURFACE

HEAT

FLUX

(W/m 2)

TEMPERATURE

DIFFERENCE

(°C)

AIR

TEMPERATURE

(°C)
SURFACE

HEAT

FLUX

(Btu/h-ft

2)

TEMPERATURE

DIFFERENCE

(°F)

AIR

TEMPERATURE

(°F)

TIME (b)

Figure 9.12 Temperature and Heat Flux in the Columbia

Building as a Function of Time

145

SURFACE

HEAT

FLUX

(W/m2)

TEMPERATURE

DIFFERENCE

(°C)

AIR

TEMPERATURE

(°C)
TIME (h)

Figure 9.13 Wall Thermal Resistance Values Plotted as a Function

of the Length of the Measurement Period for the Ann

Arbor Building

146

R-VALUE

(m

2

-K/W)
position (m)

CMEi

X3

_l

LL<

UJz

Figure 9.14 Comparison of Calculated Heat Flux on the

Inside Surface with Measured Values

POSITION (m)

60

50

40

30

20

io 5

0 <

UJZ

-to

-20

-30

Figure 9.15 Calculated Outside Surface Heat Flux Distribution

147
10. SUMMARY AND CONCLUSIONS

The application of diagnostic measurements to eight federal office

buildings revealed that, though most of these buildings were built to

energy conservation guidelines, all contained serious defects which

compromised their energy performance. Ground based thermographic surveys

showed that from 6 to 18 percent of the insulated wall areas of the

building contained thermal defects, including missing insulation, thermal

bridges, defective ceiling and floor insulation and convection within

insulation. Buildings with overhangs and indentations appear to have

severe problems in those areas. Aerial thermographic surveys performed by

private contractors on three large federal office buildings were

technically capable of detecting thermal deficiencies in the built-up roof

system of the buildings if used with a walk-on inspection of the roof.

However, the inspection of the roofs revealed a defect in only the Columbia

building. The private contractors who performed the aerial thermographic

inspections also required walk-on thermographic inspections to identify

deficiencies observed by the aerial inspections. This fact calls into

question the economy of aerial thermographic inspections unless large roof

areas or many buildings are inspected. It was not possible to collect

useful thermographic data for the inverted membrane roof of the Anchorage

federal building. Audits of office buildings with spot radiometers in

order to determine in-situ thermal resistances did not produce consistent

results. These audits did produce qualitatively correct results; however,

thermographic inspections are probably a more efficient way to obtain the same results. Tracer gas tests of the eight federal buildings determined

that the buildings experienced average air infiltration rates of 0.2 to 0.7

air changes per hour and that air infiltration accounted for 23% to 61% of

the design heat loads, being over 50% for four of the federal office

buildings. Table 10.1 gives an estimate of the components of the building

envelope to the building design load, using the measured average air

infiltration rates. Table 10.2 and figure 10.1 compare these estimated

building design loads to the FY1981 energy used for space heating

normalized to the building floor area and the degree day of the site.

Figure 10.2 shows a plot of the conductive component of the design load and

the FY1981 energy used for space heating.

Given the simple assumptions of this analysis, the correlation between the

estimated design losses and the energy consumed for space heating is

remarkable. From figure 10.2 it is clear that there is a component missing

from the design conductive losses needed to explain the energy used for

space heating. The analysis presented in tables 10.1, 10.2 and figure 10.1 seems to indicate that air infiltration almost completely explains this

missing energy component.

The whole building tightness tests of the federal office buildings showed

that per unit surface area these buildings were no tighter than typical

U.S. homes. There seemed to be a relationship between the results of the

building tightness tests and the measured air infiltration rates; however,

the model developed by Shaw and Tamura to predict air infiltration rates

using the results of the building tightness tests underpredicted the air

infiltration. The testing of the windows using a fan pressurization

technique showed that all the windows were leakier than the ASHRAE standard

for windows. However the windows leakage accounted for only about 20% of

the total building leakage. The measurement of the thermal resistance of

148
sections of the exterior envelope using heat flow meters and portable

calorimeters showed that the measured thermal resistance deviated from the

design thermal resistances by an average of 14%, with the worst case being

45%. An analysis of the heat losses due to the thermal bridges detected by

thermography in four of the federal office buildings indicated that the

thermal bridging increased the total opaque wall heat losses from 9 to 20

percent. The thermal bridging due to steel framing members increased the

heat loss by up to 30 percent.

The measured minimum ventilation rate in two of the tighter federal

buildings were only 20 and 50 percent of the ASHRAE Standard 62-1981

recommendation for office buildings with smokers. Three of the federal

office buildings had minimum ventilation rates in excess of this

recommendation by more than 20%, thus increasing the heating or cooling

requirements under extreme weather conditions.

A brief summary of the findings of the diagnostic testing of each federal

office building follows:

Anchorage

The Anchorage federal building uses about 28,500 Btu/yr*ft^ (89.8 kWh/yrm^) for space heating. This is a well constructed building which is tight

and well insulated - though air infiltration accounts for over 55% of the

building load. The major defect is the thermal bridging resulting from the

manner in which the precast panels were suspended (increasing the wall heat

loss by about 20%). The wall area in the section above the suspended

ceiling was not insulated to the same level as the wall area below the

suspended ceilings. This was done by design; however, it is not

justifiable from a heat transfer point of view. Visual inspection of the

roof showed many areas with separations and fissures in the rigid

insulation; however limited heat flow measurement did not detect a serious

reduction in thermal resistance in the roof insulation system. During the

extreme winter conditions, this building is often operated with closed

dampers during occupied periods and has ventilation rates which are only

39% of those recommended by the ASHRAE ventilation standard for a building

with smokers.

Ann Arbor

This building is a very poor energy performer. It is consuming about

132,000 Btu/yr*ft^ (416 kWh/yr-m^) for space heating. It has a high air

infiltration rate of about 0.7 air changes per hour, which accounts for

about 48% of the building heating load. The building has over 14,000 ft^

(1,300 m^) of glass area which contributes to about 26% of the heat load.

The opaque walls constitute 18% of the heat load and the roof about 8%.

About 18% of the wall area showed thermal defects when inspected by

thermography. The thermal resistances of the wall section were close to

the predicted values when the insulation was properly installed. The

design of the building resulted in thermal bridging which increased the

wall heat loss by about 8%.

149
Columbia

The Columbia federal building uses about 20,035 Btu/yr’ft^ (63.1 kWh/m^-yr)

of energy for space heating. Air infiltration accounts for about 52% of

the space heating load (0.4 air changes per hour). Air conditioning

accounts for about 23% of the electrical energy use of the building. The

building has operable windows which are quite leaky and which account for

about 31% of the building leakage. About 17% of the wall area of the

building has thermal defects, the most serious of which was air penetration

around the insulation. This was caused by the manner in which the steel

framing was installed in the building; an approximately one inch gap was left between the exterior concrete panels and the framing, and the

insulation was hung in the framing cavities. The building also had thermal

bridging which increased the heat flow through the wall by about 10%. The

manner in which the insulation was installed in the wall area about the

suspended ceiling was incorrect, allowing air movement through the

insulation and leaving exposed exterior wall uninsulated. The minimum

ventilation rate of this building was 51% above that required for an office

building with smokers, thus adding to the space conditioning loads in

extreme weather conditions.

Fayetteville

The Fayetteville federal building uses about 30,000 Btu/ft^*yr (94.5

kWh/m^-yr) for space heating. It is basically an uninsulated building

built before the federal energy conservation guidelines were developed. In

terms of energy use per unit floor area per degree day it is the second

worst performer. The space heating load consists of 48% transmission

through the opaque walls, 25% through the glass, 23% by air infiltration

(0.33 air changes per hour) and 3% through the roof. The major deficiency

of the building is the existence of large, uninsulated wall areas including

large sections of spandrel glass. The building has serious leakage

problems at the interface of the glass and spandrel walls and the

structural columns. The first and fourth floors have serious leakage in

the overhangs in the return air plenum. The building has adequate minimum

ventilation; however, the ventilation rate is strongly wind dependent,

indicating that much of the ventilation is being supplied by air leakage

and not through the outside air supply ducts.

Huron

The Huron federal building used 21,514 Btu/ft^*yr (67.8 kWh/m^-yr) for

space heating. This building is the tightest building of the eight tested,

having an air infiltration rate of 0.2 air changes per hour. The space

heating load consists of 19% transmission through the glass areas, 31%

through the opaque wall areas, 17% through the roof and 33% by air

infiltration. The framing members of the opaque wall increased the heat

flow by about 30% above the design value of the insulation. Thermal

bridging at the floor /wall interface caused another 10% increase in heat

flow through the opaque wall areas. The minimum ventilation rate of this

building was only 26% of the minimum requirements for a building with

smokers

.

150
Norfolk

The Norfolk federal building uses about 10,588 Btu/ft^'yr (33.4 kWh/m^-yr)

of electricity (on-site) for space heating. The building heat loss

consists of 27% transmission through the glass areas, 15% through the

opaque wall areas, 6% through the roof and 15% by air infiltration (0.52

air changes per hour). The building had serious defects in the insulation

in the overhangs over the garage and front entrance. The thermal

resistance of the insulated walls was only 54% of the predicted values.

The minimum ventilation rate was 90% of that recommended for an office

building with smokers.

Pittsfield

The federal building in Pittsfield, MA uses about 51,200 Btu/ft^*yr (161

kWh/m^*yr) for space heating. The largest component of the heat load is

air infiltration, accounting for 36% of the load (0.3 air changes per

hour). The opaque walls contribute about 22% of the heat transmission, the

roof 21% and the glass area 19%. The minimum ventilation rate of the

building is 90% of the requirement for a building with smokers.

Thermography showed that about 18% of the exterior wall area had defects,

the most serious being air penetration around the insulation. The measured

thermal resistance of the walls was about 13% less than the predicted

thermal resistance.

Springfield

The Springfield federal building was a newly constructed office building

and therefore there were no previous fuel records for the building.

Twenty-three percent of the heat loss of the building is due to

transmission through the glass areas, 11% through the opaque wall areas, 5%

through the roof and 61% by air infiltration (0.52 air changes per hour).

The insulation of the exterior walls consisted of rigid foam insulation

applied to the concrete panels in such a way that air could leak around the

insulation and into the air cavity between the steel framing. The

effective thermal resistance of this wall construction was only 52% of the

predicted value. The ventilation and air infiltration rates of the

building had a strong temperature dependence which could be due to the

leakiness of the building or a ventilation system control problem.

151
Table 10.1

Estimate of Above Grade Design Heat Losses (UA)

Ann Fayette- Pitts- SpringAnchorage Arbor Co lumb ia ville Huron Norfolk field field

Glass 19% 26% 27% 25% 19% 27% 19% 23%

Wall 15% 18% 16% 48% 31% 15%* 22% 11%

Roof 10% 8% 3% 3% 17% 6% 22% 5%

Air Infil - 55% 48% 42% 25% 33% 52% 37% 61%

tration

UA Btu/ 55,813 30,697 78,201 18,877 10,470 37,985 4,732 39,196

hr a F

(w/°c) (29,423) (16,183) (41,226) (9,951) (5,520) (20,025) (2,495) (20,663)

UA/Area 0.123 0.626 0.362 0.516 0.163 0.220 0.270 0.290

Btu/hr * f

2 *F)

(W/°C-m2

) (0.698) (3.552) (2.054) (2.928) (0.925) (1.248) (1.532) (1.646)

*Contains underside of overhangs.

Table 10.2

Comparison of Energy Consumed for Space Heating

versus Transmission Losses (UA)

Energy Consumed*

per Floor Area UA per Day per

per Degree Day Floor Area

Btu/day*ft 2 *°F (W/m2 -°C) Btu/day *f

2 *°F (W/m2-°C)

Anchorage 2.9 0.38 3.0 0.39

Ann Arbor 11.9 1.56 14.9 1.96

Columbia 7.8 1.02 8.7 1.14

Fayetteville 10.1 1.33 12.4 1.63

Huron 2.6 0.34 3.9 0.51

Pittsfield 6.7 0.88 7.0 0.92

Norfolk + 4.2 0.55 5.3 0.70

* Assumes 1 gal oil = 140,000 Btu (148 MJ)

1 cu ft gas = 1,000 Btu (1.05 MJ)

+ Assumes - 3,412 Btu/Kwh and 70% efficiency for other buildings.

152
MEASURED

ENERGY

PER

FT

2

PER

DEGREE

DAY

Btu/(°F-Day

• Ft

2)

10 20

W/m 2 -°C

30 40 50 60

12

10

8

• - 50

4 -

2 “

—1—1—1—1

I "i 1 1 1 1 1 1 rAnn Arbor

• Gas

Oil

Electricity

Fayetteville•

- A Columbia

- • Pittsfield

Anchorage

• m

Huron

Norfolk

1 1 1 1 l j i i i i i i i i i

- 40

30

20

10

0

4 6 8 10 12

TRANSMISSION LOSSES PER FT 2

Btu/(°F- Day - Ft 2 )

14 16

Figure 10.1 Comparison of Transmission Losses and

Energy Consumed for Each Building

153

W/m 2

- °C
MEASURED

ENERGY

PER

FT

2

PER

DEGREE

DAY

Btu/(°FDay

Ft

2)

W/m 2 -°C

0 10 20 30 40 50 60

12

10

8

6

4

2

0

0 2 4 6 8 10 12 14 16

CONDUCTION LOSSES PER FT 2

Btu/(°F • Day - Ft 2 )

1

— • Ann Arbor -

- • Fayetteville

—

A Columbia

-

• Pittsfield

• " Norfolk

Anchorage

•

• Gas

Oil

-

m

Huron Electricity

» i » i i i i i i

1 1 l 1 1 .J

50

Figure 10.2 Comparison of Conduction Transmission Losses

and Energy Consumed for Each Building

154

W/m

2o

C
REFERENCES

1. Grot, R.A., Burch, D.M., Silberstein, S., Galowin, L., "Measurement

Methods for Evaluation of Thermal Integrity of Building Envelopes,"

NBSIR 82-2506, National Bureau of Standards, Washington, DC, 1982.

2. Ouzts, K.B., Vanier, J.G., and Brotherson, D.E., "A Comparison of

Infrared Flyover, Infrared Walkover, and Visual Inspection Techniques

for Detecting Roof Moisture Anomalies," an Internal Conference on Thermal Infrared Sensing for Diagnostics and Control (Thermosense VI)

Proceedings SPIE 446, pp. 122-129, Bellingham, WA, 1983.

3. Aerial Infrared Thermography of the Federal Building, Springfield, MA,

Aeromarine Surveys, Inc., New London, CT, May 7, 1983.

4. Wallace, J.R., Thermographic Inspection Report, Wallace Thermographies

Co., Richmond, VA, June, 1983.

5. Town, R.H., "Infrared Survey for Federal Building," C Street,

Anchorage, AK. Infrared Technology of Alaska, Inc., Anchorage, AK,

No. AP6546, April, 1983.

6. Spot Radiometer Energy Audit, Federal Building in Huron, SD, Donahue

and Associates, Inc., Madison, WI, 1983.

7. Spot Radiometer Energy Audit, Federal Building in Ann Arbor, MI,

Donahue and Associates, Inc., Madison, WI, 1983.

8. ASHRAE Handbook of Fundamentals . The American Society of Heating,

Refrigerating and Air Conditioning Engineers, Inc., 1981.

9. Treado, S.J., and Burch, D.M., "Evaluation of Hand-Held Infrared

Thermometers for Wall Thermal Resistance Determination," NBSIR 79-

1736, July, 1979.

10. Burch, D.M., and Krintz, D.F., "Using High-Resolution Hand-Held

Radiometers to Measure In-Situ Thermal Resistance," in International

Conference of Thermal Infrared Sensing for Diagnostics and Control

(Thermosense VI) Proceedings SPIE 446, pp. 24-32, Bellingham, WA,

1983.

11. "Application of Infrared Sensing Devices to the Assessment of Building

Heat Loss Characteristics," ANSI/ASHRAE Standard 101-1981.

12. ASHRAE Standard 62-81, Ventilation for Acceptable Indoor Air Quality,

American Society of Heating, Refrigerating, and Air-Conditioning

Engineers, Inc., 1981.

13. ASTM E 779-81, "Standard Practice for Measuring Air Leakage by the

Fan-Pressurization Method," American Society for Testing and

Materials, 1981.

14. Kronvall, J., "Testing of Homes for Air Leakage Using a Pressure

Method." ASHRAE Transactions . Vol. 84(1), 1978.

155
15. Shaw, C.Y., Sander, D.M., Tamura, G.T., "Air Leakage Measurements of

the Exterior Walls of Tall Buildings." ASHRAE Transactions . Vol.

79(11), 1973.

16. Shaw, C.Y., "Air Tightness: Supermarkets and Shopping Malls." ASHRAE

Journal ." March 1981.

17. ASTM E 283-73, "Standard Test Method for Rate of Air Leakage Through

Exterior Windows, Curtains, Walls and Doors," the American Society for

Testing and Materials, 1973.

18. Svensson, A., "Methods for Measurement of Airflow Rates in Ventilation

Systems," Bulletin M83:ll, The National Swedish Institute for Building

Research, 1983.

19. Persily, A.K., Grot, R.A., "Air Infiltration and Building Tightness

Measurements in Passive Solar Residences," Journal of Solar Energy

Engineering . Vol. 106, No. 2, 1984.

20. Tamura, G.T., Shaw, C.Y., "Studies of Exterior Wall Air Tightness and

Air Infiltration of Tall Buildings," ASHRAE Transactions. Vol. 82(1),

1976.

21. Weidt, J.L., Weidt, J., Selkowitz, S., "Field Air Leakage of Newly

Installed Residential Windows," DoE/ASHRAE Conference on the Thermal

Performance of Exterior Envelopes of Buildings, Orlando, Florida,

December 1979.

22. Ward, I.C., Sharpies, S., "An Investigation of the Infiltration

Characteristics of Windows and Doors in a Tall Building Using

Pressurization Techniques," Report BS 68, Department of Building

Science, University of Sheffield, 1982.

23. Tamura, G.T., "Measurement of Air Leakage Characteristics of House

Enclosures." ASHRAE Transactions . Vol. 81(1), 1975.

24. Shaw, C.Y., Tamura, G.T., "The Calculation of Air Infiltration Rates

Caused by Wind and Stack Action for Tall Buildings," ASHRAE

Transactions . Vol. 83(11), 1977.

25. Hunt, C.M., Treado, S.J., "Air Exchange Measurements in a High-Rise

Office Building," DoE/ASHRAE Conference on the Thermal Performance of

Exterior Envelopes of Buildings, Orlando, FL, December, 1979.

26. ASTM C 177-76, "Standard Test Method for Steady-State Thermal

Transmission Properties by Means of the Guarded Hot Plate," the

American Society for Testing and Materials, 1976.

27. Powell, F.J., Rennex, B.J., "NBS Line-Heat-Source Guarded Hot Plate

for Thick Materials," Proceedings of the ASHRAE/DoE Conference on Thermal Performance of the Exterior Envelopes of Buildings II . Las

Vegas, NV, ASHRAE SP 38, December, 1982.

28. Brown, W.C. and Schuyler, G.D., "In-Situ Measurements of Frame Wall

Thermal Resistance." ASHRAE Transactions . Vo. 88(1), 1982.

156
29 . Brown, W.C. and Schuyler, G.D., "A Calorimeter for Measuring Heat Flow

Through Walls," Proceedings of the ASHRAE/DoE Conference on Thermal

Performance of the Exterior Envelopes of Buildings . Kissimmee, FL,

ASHRAE SP 28, December, 1979.

30. Granum, H., "The Role of the Building Envelope," in 'Building Research

World Wide,' edited by the Norwegian Research Institute, 1980.

31. Elrod, D.C., Giles, G.E. and Turner, W.D., "HEATING6: A

Multidimensional Heat Conduction Analysis with the Finite-Difference

Formulation," Union Carbide Corporation, Nuclear Division,

0RNL/NUREG/CSD-2/V2, Oak Ridge, TN, October, 1981.

157
Appendix A

Economic Methodology

for Selecting Optimal Energy Diagnostic Techniques

for Federal Office Buildings

Because application of the various energy diagnostic techniques discussed

in the previous chapters of this report causes the user to incur costs, a method is needed to decide whether such expenditures are economically

justified. The purpose of this chapter is to describe and illustrate an economic methodology that addresses two types of decisions: (1)

determining whether a particular diagnostic technique is cost effective for

a given federal office building; and (2) selecting the most cost-effective

technique from among a set of techniques, any one of which could be applied

to a particular building or building component. The first type of decision

arises when there is only one diagnostic technique worth considering for a particular application. This situation may prevail because economic or technical considerations limit the availability of alternative techniques.

The second type of decision arises when more than one technique can be

considered for an application, and they differ either in their associated

costs or benefits.

A.l. Data Requirements

Implementation of the economic methodology presented in this section

depends on the availability of two types of data: (1) cost data and (2)

benefits data.

A. 1.2 Cost Data

The cost data required for the methodology include all expenditures

associated with carrying out each diagnostic technique being studied. The

major cost items that need to be taken into account are specified in the

Cost Data Collection Form for Diagnostic Tests presented in exhibit A.l.

The significant distinction to be observed on this form is the one that

exists between fixed and variable costs. Item 2 covers fixed costs, which

are defined as those costs that are invariant with respect to the size of

the building component being diagnosed. The primary examples of fixed

costs are those arising from the transport of equipment, materials, and

personnel to and from the building site. In addition, equipment costs

(item 4) frequently tend to be fixed costs whenever the size and number of

pieces of equipment do not have to be tailored to the size of the component

being diagnosed.

Variable costs of the diagnostic technique are listed under item 3. These

costs, such as for labor and materials, tend to vary in proportion to the

size of the building component being diagnosed.

The background data covered in item 1 on the form include the component

size, which quantifies how many physical units the particular diagnostic

test is to cover for the building in question. The physical unit of

measure chosen to represent size in this sense should be the unit that most

directly affects the costs of the diagnostic test. This

158
Exhibit A.l

1 . 1.1

1.2

1.3

1.4

1.5

2 .

2.1

a

.

b.

2.2

a

.

b.

c . 2.3

a.

b.

c

.

3 .

3.1

a.b.

c

.

d.

3.2

a.b.

c

.

d.

e . 3.3

a

.

COST DATA COLLECTION FORM FOR DIAGNOSTIC TESTS

GENERAL BACKGROUND DATA

Date of Test:

Building Name and City:

Diagnostic Technique:

Component Diagnosed:

[Give name or description of component whose energy-related

performance is being diagnosed.]

or Component Size: ? [Express size of component in whatever physical units (i.e., f, f" f^ most directly affect the costs of the diagnostic test.]

FIXED COSTS OF DIAGNOSTIC TEST

[Fixed costs are invariant with respect to size of component

diagnosed.

]

Transport of Equipment and Materials to and From Site

Packing, Shipping, Insurance:

Time in Transit:

Personnel Transport to and From Site

Air, Train Fare:

Local mileage or vehicle rental fee:

Time in transit:

Special Factors Affecting Fixed Costs

Crew size:

Number and weight of pieces of equipment:

Other? :

VARIABLE COSTS OF DIAGNOSTIC TEST

[Variable costs tend to vary in proportion to the size of component

diagnosed.

]

Labor at Site

[itemize crew members by skill category and give hours worked and

hourly wage for each category.]

Skill type:

Hours : Wage ($/hr):

Total cost:

Materials

[Itemize each material or energy type used and give the quantity and

unit cost of each; also indicate whether the item is reusable by

entering the number of times the item is customarily used (i.e., if

not reusable, enter 1).]

Material:

Quantity:

Unit cost:

Total cost:

Times Usable:

Special Factors Affecting Variable Costs

Type of heating /coo ling equipment:

[Give features of equipment which affect variable costs, such as the

size, number of units, location of units, and distance apart.]

159
Exhibit A.l (continued)

b. Other:

4. EQUIPMENT

[Describe each piece of diagnostic equipment used (4.1). Give current

cost of purchasing equivalent equipment (4.2), the number of years of

expected useful service life (4.3), the average number of site visits

in a typical year (4.4), and the maintenance and repair costs per year

(4.5). As an alternative to (4.2) through (4.5), given the equivalent

rental rate per visit (4.5).]

Equipment #1 Equipment #2 Equ ipment #3

4.1

Description

4 . 2 Current Cost

($)

4.3 Life (Yrs)

4.4 Visits

(#/Yr)

4.5 M&R Cost

($/Yr)

[4.6 Rent

($/Visit)]

160
component size variable is the physical dimension to which the variable

cost items are expected to be approximately proportional. Under this

assumption of variable cost proportionality, total diagnostic costs can be

modelled as a linear function of the component size variable. The

algebraic expression for this function is:

C = F + V * S, (A. 1)

where C = a variable representing total costs of the diagnostic test for

the component ($);

F = a parameter representing fixed diagnostic test costs, i.e. costs

which are invariant with respect to component size ($);

V = a parameter representing variable diagnostic test costs, i.e.

costs which vary in proportion to component size ($/unit); and

S = a variable representing component size, measured in physical

units (units).

Given a statistically valid sample of data on the variables, C and S, for

each diagnostic technique, it is possible to derive reasonably precise,

unbiased estimates of the parameters, F and V, using standard least squares

regression methods. Alternatively, if only a small sample of cost data is

available with information on each cost item as specified in exhibit A.l,

then approximate values for the parameters F and V can each be directly

derived from the separate data on Fixed and Variable Costs, respectively.

This alternative procedure for deriving F values involves first summing all

the costs under item 2 (Fixed Costs) and adding to that sum all those cost

entries listed under item 4 (Equipment) which are not expected to vary as a function of S (1). This first step must be carried out for each building

sampled for the diagnostic technique in question. These Fixed Cost values

must then be averaged across all the buildings in the sample to obtain the

F value. Similarly, an approximate value for the parameter V can be found

by first totaling the Variable Costs under item 3 of exhibit 1 and adding

to this total all those cost entries from item 4 (i.e., Equipment) which

are expected to vary in proportion to S. This Variable Cost value is to be

computed for each building and then averaged across all buildings sampled

to arrive at the approximate value of V.

Whichever method is used to estimate the values of the parameters, F and V,

it must be assumed that both parameters will be fairly constant for a given

diagnostic technique. This is, a single value can be assigned to F and a single value can be assigned to V for a given technique. Moreover, because

economic resources must be used to carry out the diagnostic tests.

(1) Because most capital equipment is "lumpy" (i.e., it comes in limited,

discrete sizes) rather than continuously variable, the cost entries under

item 4 will usually be included in the cost function a6 part of fixed

costs, F. If the range of interest in the analysis extends beyond the

capacity of one discrete size of equipment, then the cost function becomes

a step function and discontinuous at endpoints of the equipment capacity

ranges

.

161
the value of C in expression (A.l) is positive. This means that either F or V must be positive (since Component Size, S, is positive. Indeed, it is

reasonable to expect that the true values of both F and V for most

diagnostic techniques are positive. Based on this information regarding

the probable ranges of values for F and V, the linear relationship between

C and S given in expression (A.l) can be illustrated graphically as shown

in exhibit A. 2.

A. 1.3 Benefits Data

The benefits data needed to implement the methodology are basically derived

from an economic comparison of two situations: (1) retrofitting the

building for energy conservation according to the recommendations that

result from the application of the diagnostic technique; and (2)

retrofitting the building without the benefit of the specific information

or recommendations derived from the diagnostic technique. This economic

comparison is conducted in terms of the discounted present values of the

net dollar savings (i.e., energy cost reductions minus the cost of

retrofitting) from the two sets of energy conservation retrofits. In other

words, the benefits of a diagnostic technique are based on the discounted

present value of the net dollar savings over the remaining life of the

building that are directly attributable to applying the technique.

The first 6tep involved in estimating the present value of the net savings

attributable to each diagnostic technique is to identify the two sets of

all mutually compatible energy conservation retrofit options that would be

considered for economic evaluation both in the absence and in the presence

of the technique. Which retrofit options are identified in this process

would be influenced generally by the type of building, the fuel used for

heating and cooling, and the climatic conditions of the geographic

location. For each of the candidate retrofit options identified, economic

data must be collected as specified in exhibit A. 3. Once the necessary

economic data have been gathered, a life-cycle cost (LCC) evaluation of

each retrofit option must be conducted along the lines described in LifeCycle Costing Manual for the Federal Energy Management Program (2). The

result of the LCC evaluation should then be compared with a benchmark LCC

evaluation of installing no retrofits at all. If the LCC of the retrofit

option is greater than that of the benchmark, the retrofit should not be

installed. If the LCC of the retrofit is less than that of the benchmark,

then the difference between the two LCC values represents the net savings

attributable to that retrofit option. The sum of these positive net

savings estimates across all retrofit options that would be installed

(i.e., those options considered that were found to have LCC values less

than that of the benchmark) in the presence of the diagnostic technique

must be compared with the sum of the corresponding positive net savings across all the retrofit options that would be installed in the absence of

the diagnostic technique. The difference between these two sums represents

an estimate of the net savings directly attributable to the application of

the diagnostic technique. This net savings estimate will be referred to as the Benefits (B) of the technique.

(2) Rosalie T. Ruegg, Life-Cycle Costing Manual for the Federal

Energy Management Programs . National Bureau of Standards Handbook 135

(Revised May, 1982), Washington, DC: U.S. Department of Commerce, 1982.

162
Exhibit A.

2

Cost (C) of Applying a Diagnostic Technique as a Linear

Function of Building Component Size (S)

163
Exhibit A.

3

ECONOMIC DATA SHEET FOR GSA RETROFIT OPTIONS

1. Building Name 2. City

3. Component 4. Date

Option #1 Option #2

5.

Specifications

6. Scaffolding Needs (Check One)

a. None (Inside access)

b. Swing (Suspended)

c. Stage (Built-Up)

7. Max. Working Dist. (f)

(Omit if 6. a is checked)

8. Job Dimensions

Length (f)

Area (f^)

Sizes (f x f)

Number

9. Expected Cost ($)

10. Expected Life (yrs.)

11. Expected Reduction in

Annual Purchased Energy

Oil (Gal./yr.)

Gas ( Therms /yr.)

Electric (kWh/yr.)

12. Additional Comments

164
Exhibit A. 3 (continued)

General Instructions:

Use a separate data sheet for each building component to be

retrofitted. If there are more than two retrofit options to be

considered for a particular building component, use additional data

sheets

.

Items 1 and 2: Fill in the name of the building and the city in which it

is located.

Item 3: Indicate which building component is to be retrofitted, e.g.,

roof, exterior walls, doors, windows. Be sure to use a separate

sheet for each component.

Item 4: Today's date.

Item 5: Give a detailed description of the retrofit work to be done under

each option. Specify the type, thickness, and quality of all

materials to be used, give the tolerances and performance

specifications to be met, and also indicate any special

circumstances of the job that might affect materials or labor

costs (e.g., whether the retrofit work area will be occupied by

office workers). Attach separate, if necessary.

Item 6: Indicate whether and what type of scaffolding will be required.

If all the work can be done from the inside, check 6. a. If swing

scaffolding that is suspended from the top of the building wall

can be used, check 6.b. If stage scaffolding that is built-up

from the ground is needed, check 6.c.

Item 7: Indicate the maximum required working distance (f) from the top

of the building to the work area for swing scaffolding (6.b), or from the ground to the work area for stage scaffolding (6.c.).

Item 8: Indicate in detail the complete dimensions of the retrofit job.

For caulking and weatherstripping, give the crack length, in feet

(f); for walls and roofs, give the area in square feet (f^); and

for windows and doors, give both the height and width of each

different size, in feet (f), as well as the number of windows and

doors of each size. Attach separate sheet if necessary.

Item 9: Give a rough estimate of the total cost of the retrofit option

for that component, if the work were done today under a union

contract

.

Item 10: Give the expected life of the retrofit, of the building

component, or of the entire building, whichever is shortest.

165
Exhibit A. 3 (continued)

Item 11: Estimate the reduction in annual purchased energy expected to

result from this retrofit option being applied to this building

component. Be sure to state estimated savings in terms of units

of purchased energy, rather than in terms of changes in heating

or cooling loads. These purchased energy savings should be given

in gallons of fuel oil, therms of natural gas, kilowatt-hours of

electricity, or some combination of these three. If demand

charges are expected to be affected, indicate the reduction in

kilowatts expected for each billing period (month) affected.

Item 12: Provide any additional information that might affect the costs or benefits of the retrofit option. If any local building

contractor has been identified as capable of accomplishing the

retrofit, please given name and phone number. Also information

on which local utility companies serve the building would be

helpful, as would the name and phone number of the building

engineer or superintendent.

166
Once sufficient Benefits data have been collected for a particular

technique over a range of building component sizes, an explicit

relationship can be derived between Benefits and component size. It is

expected that this relationship could be represented reasonably well by the

following algebraic expression:

B = P * S , (A. 2)

where B = a variable representing the estimated Benefits of the diagnostic

technique for the building component ($);

P = a parameter representing the combined effects on B resulting from

local climatic factors, the cost of energy, the discount rate,

and the conversion efficiencies of the mechanical equipment

($/unit); and

S = a variable representing building component size, measured in

physical units (units).

The value of P for a given building will depend on the local climatic

factors affecting the building energy use, the current and projected future

cost per unit of purchased energy, and the heating and cooling conversion

efficiencies of the mechanical equipment used in the building. For a specific building in a particular location, these factors are held fixed,

so that the value of P would not change because of them. Another important

factor affecting the value of P is the discount rate used to compute the

LCC values of the retrofit options on which the estimate of B is based.

The discount rate can be considered as a constant even in the analysis of

several different Federal buildings since a common rate of seven percent is

prescribed for evaluating energy conservation investments under the Federal

Energy Management Programs. Consequently, P can be considered as a positive constant for any particular building and diagnostic technique.

This means that the general relationship given in expression (A.2) can be

illustrated graphically as shown in exhibit A. 4.

A.2. Evaluation of a Single Diagnostic Technique

The first type of decision addressed by this methodology concerns the case

in which there is only one diagnostic technique available that can be

reasonably applied to the particular building component being analyzed.

This situation would arise when there simply is only one technique or when

one technique clearly dominates all the others with respect to ease of

application, effectiveness, and cost. The basic objective of the

methodology in such a case would be to determine whether the single

technique is expected to yield sufficient economic benefits to cover the

costs of applying the diagnostic technique. As has been shown, both the

benefits and costs of the technique can be expressed as functions of a common variable, the size of the building component being analyzed. The

methodology takes advantage of this fact by determining the breakeven value

of this common variable. That is, the methodology finds that critical

value of the building component size below which the diagnostic technique

is not cost effective, and above which it is cost effective. As an illustration, this type of analysis is graphically depicted in exhibit A.

5

for air infiltration measurements using the diagnostic technique of tracer

gas decay.

167
As can be seen in exhibit A. 5, both the benefits and costs of using the

tracer gas dilution method to measure air infiltration are functions of the

volume of the enclosed space in the building. Because of the presence of

positive fixed costs and the proportional nature of the benefits function,

the building component sizes (i.e., in this case, the volume of the

building) to the left of (or less than) the Breakeven (BE) volume at which

the two curves intersect, the costs of this diagnostic technique exceed its

expected benefits. For this range of smaller building volumes, therefore,

the technique was found not to be cost effective. In contrast, for

building volumes greater than BE, the benefits exceed the costs, making the

technique cost effective in this larger building volume range. This BE

value will always occur in the positive range of building component sizes, as long as two conditions are fulfilled: (1) the slope of the benefits

function must exceed that of the cost function (i.e., P > V), and (2) there

mut be positive fixed costs (i.e., F > 0). If the first of these

conditions is not met, then there is no positive BE value, and the

diagnostic technique being evaluated can be said not to be cost effective

over the entire range of building component sizes. In other words, without

a positive BE value, the technique would not be cost effective for any

building size. If the first condition is met while the second condition is

not, then the BE value would occur at the origin, which would mean that the

diagnostic technique is cost effective for all building component sizes.

A. 3. Evaluation of Alternative Diagnostic Techniques

The second type of decision addressed by this methodology concerns the case

in which there is more than one diagnostic technique available to be

applied to the analysis of a particular building component. The objective

of the methodology in this case is to find the technique which would yield

the greatest benefits net of costs for the size of building component being

analyzed. To accomplish this, expression (1) should be subtracted from

expression (2) for each of the diagnostic techniques to be compared in

order to form a combined expression for the Net Benefits (NB):

NB=B-C=P*S-F-V*S=-F + (P-V) * S, (A. 3)

where all of the variable and parameters are as previously defined. This

expression is to be evaluated for the building component size being studied

and then the technique with the highest value of NB is the one that should

be chosen. Because F is a positive constant, the intercept of NB will be

negative, which means that for the lowest range of building component size

there will be no diagnostic technique that is cost effective. Because the

values of F and of the slopes of expression (A. 3) are likely to be

different for each diagnostic technique, there will be breakpoints

separating the ranges of component size for which a particular technique

has the highest NB. This is graphically illustrated with hypothetical data

for the case of two diagnostic techniques in exhibit A. 6. As can be seen

from the graph, neither of the techniques is cost effective for the lowest

range (i.e., below 19 thousand sf) of building envelope size. In the

middle range of building envelope size (i.e., between 19 and 50 thousand

sf), the spot radiometry method yields the highest value of NB, and in the

highest range (i.e., above the breakpoint at 50 thousand sf), the heat flow

meter method becomes more cost effective. The economic evaluation of more

than two alternative diagnostic techniques is conducted in a similar

manner.

168
COST,

BENEFITS

($)

BENEFITS

($)

Exhibit A.

4

Benefits (B) of Applying a Diagnostic Technique as a Proportional Function of Building Component Size (S)

COMPONENT SIZE (UNITS)

Exhibit A .

5

Economic Analysis of a Single Diagnostic Technique:

Air Infiltration Measured by Tracer Gas

BUILDING VOLUME (CF)

169
Exhibit A.

6

Economic Analysis of Two Alternative Diagnostic Techniques:

Conduction Measured by Heat Flow Meters or Spot Radiometry

10 20 30 40 50 60 70 80 90 100 110

BUILDING ENVELOPE RRER (1000 SF)

170
Appendix B

Specifications for Aerial Infrared Thermography

Roof Inspections

1 . Guidelines and Requirements

Scope - Aerial Thermographic surveys will be performed by fixed wing or helicopter with suitable equipment for airborne measurement procedures.

The contractor(s) will be required to visit and inspect the building(s)

selected for the aerial thermographic survey. The aerial thermographic

survey will be conducted in a manner consistent with the requirements

indicated, part 3. The aerial surveys will be performed in such a manner

as to result in production of photographic, TV film and/or other

documentation of the infrared data from such inspections with sufficient

detail to permit the identification and location of defects and thermal

anomalies for each building. A conventional aerial photograph(s) should

bee taken during daylight hours of the same scene displayed in the thermal

image

.

The contractors ) will prepare and transmit a reproducible report which

will contain a comprehensive detailed description of the inspection survey,

methods and procedures for data collection, the photographic and other data

or information derived, analysis and interpretation of the survey, and

recommendations for remedial actions.

The contractor(s) will conduct the survey within a reasonable time period

when the building(s) are heated and the roof is clear of water, dew, snow

or ice. The survey, when conducted under clear sky conditions, may have

ambient air temperature differences of 30°F (17°C) below the building

interior air temperature; for other than clear sky conditions the

temperature difference should be at least 40°F (22°C). For all cases, the

outside ambient air temperature should not exceed 45°F (7°C). The survey

should be at least four hours after sunset, sky conditions homogeneous, and

wind speed less than 15 mph (7 m/s).

The spatial resolution of the scanner shall be one foot square (object

plane resolution at the flight path nadir). The actual usable field of

view shall not exceed +. 45° with respect to the flight path nadir.

A method of displaying the scanner video signal or thermal map to the

operator to facilitate proper settings of controls. Data may be recorded

directly on hard copy film or other medium in analog or digital form

suitable for processing by the contractors ) into hard copy thermograms.

Two internal black body reference sources are desired for the line scanner

to display radiance temperature range in the thermal image. Instrument

sensitivity requirements for anticipated minimum resolvable temperature

difference (MRTD) shall be indicated in the proposal for exterior (air)

temperatures and wind speeds in the vicinity of the building(s).

171
Operation and Data Record - Scanners should be operated within aircraft

speed and altitude envelopes to provide the required resolution,

continguous line scanning (or overscanning) or building roof surfaces.

Undesirable motions should not seriously degrade the thermal image.

The following data should be recorded:

1. Date of survey

2. Time of survey

3. Outdoor ground-level temperature

4. Wind speed at ground level

5. Sky conditions (i.e., clear, solid overcast, etc.)

6. Flight line location and orientation

7. Approximate ground speed and altitude of aircraft

8. Site conditions (i.e., foliage, roofs having low emittance ,etc .

)

Staff Qualifications - Aerial infrared thermography should be undertaken by

trained personnel. The training requirements are similar to those of level

II in the Canadian training program*. The interpretation of aerial

thermograms must take into account overflight conditions, environmental

conditions at the time of data collection, and knowledge of the particular

structure and surface conditions (dry, wet, etc.).

Experience and/or Capabilities - The organization and staff that will

participate in the project shall be described in sufficient detail to

enable evaluation of capabilities to perform the proposed effort. For the

purpose of the evaluation of the proposals on a competitive basis the

information provided to accomplish the inspection, survey, report,

staffing, organization qualifications, and costs will be weighed as factors

in determining the contract award(s).

2. Exceptions

Exceptions to any lists, guidelines or requirements may be permitted

provided that explanation describing consistency with good commercial

practices or experiences are provided as a basis for technical evaluation

by NBS.

*Public Works Canada Training, Level I (thermographic), Level II

(Thermographic), Level III (Building Science).

172
3 . Use of Other Equipment

Where the normal commercial roof survey and inspection processes require

other devices, instruments or integral for inspections with roof analysis

services beyond infrared aerial measurement methods such equipment and

their intended purposes shall be stated in the proposal and reported on in

the final document, when used in this investigation.

173
Appendix C

Specifications for Energy Audits with Spot

Radiometers for Temperature or Radiosity Measurements

1 . Guidelines and Requirements

Scope - Conduct public building energy audits with measurements utilizing

temperature or radiosity spot radiometers, perform data analysis and

interpretation of measurements and audits to determine deficiencies in

smaller federal buildings, prepare remedial actions recommendations, and

submit a report documenting the results for:

o Estimated heat loss from major building components

o Thermal anomalies and deficiencies

o Identified measures for energy saving retrofits

The contractor(s) will prepare a reproducible report which will contain a comprehensive detailed description of the inspection survey, use of spot

radiometers, the methods and procedures for data collection, data,

photographic and other appropriate information derived for analysis,

calculations and interpretation of the survey and recommendations for

remedial actions.

The contractor(s) will be required to visit and inspection the building(s)

selected for the audits and measurements. The inspections, audits and

measurements will be conducted in a manner consistent with the requirements

indicated, part 3. The audits and measurements will be performed in such a manner as to result in reproducible format data sheets, or other records,

with sufficient detail and summary findings developed onsite to permit

independent review and analysis of the results, location of defects and

anomalies and heat loss estimation.

The contractor(s) will conduct the audits and measurements within a reasonable time period when the building(s) are heated. The indoor-tooutdoor temperature difference shall exceed 18°F (10°C). The building

heating plant shall be turned off 30 minutes prior to the measurements.

The measurements should not be carried out sooner than three hours after

sunset. Interior shading devices should be closed. A suitable calibration

method shall be provided; accurate outdoor temperature measurement by

thermometer is required.

Requirements - The contractor(s) shall provide the proposed (blank) spot

radiometer data record and audit format sheets to be applied for the audit

measurement inspections. Conduct the building(s) survey in accordance with

the following provisions:

174
Equipment Specifications

Temperature spot radiometer resolution to within +. 0.5°F (0.3°C).

Tabulation of uncertainties as a percent error in measuring the

thermal resistance of walls and measurements of temperature

differences are to be provided in the proposal.

Reference surface provisions for calibrating the radiometer shall be

provided and described.

The technique for determination of equivalent black body (reflected

radiation) reference temperature measurement of the surroundings

shall be provided and described.

Auxiliary temperature measurement for thermal resistance determination

with radiosity equipment is required.

Operation and Data Record - The radiometers should be calibrated with

reference surfaces provided by manufacturers or comparable methods. Data

on prepared formats should be recorded to show:

1. Date, time and location of inspection.

2. Measured values from instruments.

3. Outdoor temperature and wind conditions.

4. Site weather conditions.

5. Audit inspection findings.

6. Photographs of observable defects.

Staff Qualifications - Audits with spot radiometers inspection survey and

measurements should be undertaken by personnel trained as energy auditors

and have training to level I for a paraprof ess iona 1 as indicated by the

Canadian Training Program.*

Experience and/or Capabilities - The organization and staff that will

participate in the project shall be described in sufficient detail to

enable evaluation of capabilities to perform the proposed effort with spot

radiometers. For the purpose of the evaluation of the proposals on a competitive basis the information provided to accomplish the inspection,

survey, report, staffing, organization qualifications, and costs will be

weighed as factors in determining the contract award(s).

2. Exceptions

Departure from any listed guidelines or requirements may be permitted

provided that spot radiometers will not be made subordinate to other

equipment, devices or imaging techniques categorized as essential equipment

to conduct an instrumented audit inspection. The supporting rationale must

be technically valid and reflect a high quality level for good commercial

practices or from experience, and provided as a basis for evaluation to

NBS.

Public Works Canada Training Program, Level I (Thermographic), Level II (Thermographic), Level III (Building Science).

175
3 . Use of Other Equipment

Where normal commercial audit practice requires other supplementary

devices, instruments regarded as integral for inspections such equipment

and their intended purposes are to be described, stated in the proposal and

reported on in the final document, when used in this investigation.

*U.8. GOVERNMENT PRINTING OFFICE: 1985 491 097 36664
FOAM NBS-1 1 4A (REV n 84) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 85-3147

2. Performing Organ. Report No. 3. Publ ication Date

SEPTEMBER 1985

4. TITLE AND SUBTITLE

Evaluation of the

Building Envelopes

Thermal Integrity of the

of Eight Federal Office Buildings

5. author(S) Richard A. Grot, Andrew K. Persily, Y. May Chang, Jin B. Fang,

Stephen Weber and Lawrence S. Galowin

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State, ZIP)

General Services Administration

18th and F Streets

Washington, DC 20405

10.

SUPPLEMENTARY NOTES

J Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) Diagnostic test methods were applied to eight federal office buildings in order to assess the applicability to these measurement methods for determining the thermal

integrity of the building envelope. The eight federal office buildings were located in

Anchorage, AK; Ann Arbor, MI; Columbia, SC; Fayetteville, AR; Huron, SD; Norfolk, VA;

Pittsfield, MA and Springfield, MA. These buildings ranged in size from 20,000 ft

(1,900 m

2

) for the building in Pittsfield to 520,000 ft 2 (48,000 m

z

) for the Anchorage

federal building. They were all constructed within the last ten years. The diagnostic

tests which were applied to these buildings were ground infrared thermographic inspection, aerial infrared thermographic inspection, spot radiometry , air infiltration and

ventilation rate measurement using tracer gas decay, building tightness testing us.... fan pressurization, component tightness testing, and measurement of the thermal con- ductance of major wall sections using portable calorimeters and heat flow meters. inis

report presents and discusses the results of these tests.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate v-c'Cs t, Air infiltration; building diagnostics; building thermal integrity, fan prcssuri ;:.it ; field measurements; spot radiometers; thermal bridges; thermographic inspect ion;

tracer gas techniques; U-value measurements.

13.

AVAILABILITY

[X] Unlimited

| | For Official Distribution. Do Not Release to NTIS

H Order From Superintendent of Documents, U.S. Government Printing Office, Washington. D( 20402.

[X] Order From National Technical Information Service (NTIS), Springfield, VA 2216 1

14. NO. OF

PRINTED PAGES

200

15. P

It «OM


1